embedaddon/libxml2/result/valid/REC-xml-19980210.xml - view

File: [ELWIX - Embedded LightWeight unIX -] / embedaddon / libxml2 / result / valid / REC-xml-19980210.xml
Revision 1.1.1.1 (vendor branch): download - view: text, annotated - select for diffs - revision graph
Tue Feb 21 23:38:02 2012 UTC (12 years, 4 months ago) by misho
Branches: libxml2, MAIN
CVS tags: v2_9_1p0, v2_9_1, v2_8_0p0, v2_8_0, v2_7_8, HEAD

libxml2

1: <?xml version="1.0" encoding="ISO-8859-1" standalone="no"?> 2: <!DOCTYPE spec SYSTEM "dtds/spec.dtd" [ 3: <!ENTITY XML.version "1.0"> 6: <!ENTITY doc.date "10 February 1998"> 7: <!ENTITY iso6.doc.date "19980210"> 8: <!ENTITY w3c.doc.date "02-Feb-1998"> 9: <!ENTITY draft.day "10"> 10: <!ENTITY draft.month "February"> 11: <!ENTITY draft.year "1998"> 12: <!ENTITY WebSGML "WebSGML Adaptations Annex to ISO 8879"> 13: <!ENTITY lt "<"> 14: <!ENTITY gt ">"> 15: <!ENTITY xmlpio "'<?xml'"> 16: <!ENTITY pic "'?>'"> 17: <!ENTITY br "\n"> 18: <!ENTITY cellback "#c0d9c0"> 19: <!ENTITY mdash "--"> 20: <!ENTITY com "--"> 21: <!ENTITY como "--"> 22: <!ENTITY comc "--"> 23: <!ENTITY hcro "&#x"> 24: <!ENTITY nbsp " "> 25: <!ENTITY magicents "<code>amp</code>, 26: <code>lt</code>, 27: <code>gt</code>, 28: <code>apos</code>, 29: <code>quot</code>"> 30: <!ENTITY doc.audience "public review and discussion"> 31: <!ENTITY doc.distribution "may be distributed freely, as long as 32: all text and legal notices remain intact"> 33: ]> 34:  35: <?VERBATIM "eg" ?> 36: <spec> 37: <header> 38: <title>Extensible Markup Language (XML) 1.0</title> 39: <version/> 40: <w3c-designation>REC-xml-&iso6.doc.date;</w3c-designation> 41: <w3c-doctype>W3C Recommendation</w3c-doctype> 42: <pubdate><day>&draft.day;</day><month>&draft.month;</month><year>&draft.year;</year></pubdate> 43: 44: <publoc> 45: <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;"> 46: http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;</loc> 47: <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.xml"> 48: http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.xml</loc> 49: <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.html"> 50: http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.html</loc> 51: <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.pdf"> 52: http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.pdf</loc> 53: <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.ps"> 54: http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.ps</loc> 55: </publoc> 56: <latestloc> 57: <loc href="http://www.w3.org/TR/REC-xml"> 58: http://www.w3.org/TR/REC-xml</loc> 59: </latestloc> 60: <prevlocs> 61: <loc href="http://www.w3.org/TR/PR-xml-971208"> 62: http://www.w3.org/TR/PR-xml-971208</loc> 63:  74: </prevlocs> 75: <authlist> 76: <author><name>Tim Bray</name> 77: <affiliation>Textuality and Netscape</affiliation> 78: <email href="mailto:tbray@textuality.com">tbray@textuality.com</email></author> 79: <author><name>Jean Paoli</name> 80: <affiliation>Microsoft</affiliation> 81: <email href="mailto:jeanpa@microsoft.com">jeanpa@microsoft.com</email></author> 82: <author><name>C. M. Sperberg-McQueen</name> 83: <affiliation>University of Illinois at Chicago</affiliation> 84: <email href="mailto:cmsmcq@uic.edu">cmsmcq@uic.edu</email></author> 85: </authlist> 86: <abstract> 87: The Extensible Markup Language (XML) is a subset of 88: SGML that is completely described in this document. Its goal is to 89: enable generic SGML to be served, received, and processed on the Web 90: in the way that is now possible with HTML. XML has been designed for 91: ease of implementation and for interoperability with both SGML and 92: HTML. 93: </abstract> 94: <status> 95: This document has been reviewed by W3C Members and 96: other interested parties and has been endorsed by the 97: Director as a W3C Recommendation. It is a stable 98: document and may be used as reference material or cited 99: as a normative reference from another document. W3C's 100: role in making the Recommendation is to draw attention 101: to the specification and to promote its widespread 102: deployment. This enhances the functionality and 103: interoperability of the Web. 104: 105: This document specifies a syntax created by subsetting an existing, 106: widely used international text processing standard (Standard 107: Generalized Markup Language, ISO 8879:1986(E) as amended and 108: corrected) for use on the World Wide Web. It is a product of the W3C 109: XML Activity, details of which can be found at <loc href="http://www.w3.org/XML">http://www.w3.org/XML</loc>. A list of 110: current W3C Recommendations and other technical documents can be found 111: at <loc href="http://www.w3.org/TR">http://www.w3.org/TR</loc>. 112: 113: This specification uses the term URI, which is defined by <bibref ref="Berners-Lee"/>, a work in progress expected to update <bibref ref="RFC1738"/> and <bibref ref="RFC1808"/>. 114: 115: The list of known errors in this specification is 116: available at 117: <loc href="http://www.w3.org/XML/xml-19980210-errata">http://www.w3.org/XML/xml-19980210-errata</loc>. 118: Please report errors in this document to 119: <loc href="mailto:xml-editor@w3.org">xml-editor@w3.org</loc>. 120: 121: </status> 122: 123: 124: <pubstmt> 125: Chicago, Vancouver, Mountain View, et al.: 126: World-Wide Web Consortium, XML Working Group, 1996, 1997. 127: </pubstmt> 128: <sourcedesc> 129: Created in electronic form. 130: </sourcedesc> 131: <langusage> 132: <language id="EN">English</language> 133: <language id="ebnf">Extended Backus-Naur Form (formal grammar)</language> 134: </langusage> 135: <revisiondesc> 136: <slist> 137: <sitem>1997-12-03 : CMSMcQ : yet further changes</sitem> 138: <sitem>1997-12-02 : TB : further changes (see TB to XML WG, 139: 2 December 1997)</sitem> 140: <sitem>1997-12-02 : CMSMcQ : deal with as many corrections and 141: comments from the proofreaders as possible: 142: entify hard-coded document date in pubdate element, 143: change expansion of entity WebSGML, 144: update status description as per Dan Connolly (am not sure 145: about refernece to Berners-Lee et al.), 146: add 'The' to abstract as per WG decision, 147: move Relationship to Existing Standards to back matter and 148: combine with References, 149: re-order back matter so normative appendices come first, 150: re-tag back matter so informative appendices are tagged informdiv1, 151: remove XXX XXX from list of 'normative' specs in prose, 152: move some references from Other References to Normative References, 153: add RFC 1738, 1808, and 2141 to Other References (they are not 154: normative since we do not require the processor to enforce any 155: rules based on them), 156: add reference to 'Fielding draft' (Berners-Lee et al.), 157: move notation section to end of body, 158: drop URIchar non-terminal and use SkipLit instead, 159: lose stray reference to defunct nonterminal 'markupdecls', 160: move reference to Aho et al. into appendix (Tim's right), 161: add prose note saying that hash marks and fragment identifiers are 162: NOT part of the URI formally speaking, and are NOT legal in 163: system identifiers (processor 'may' signal an error). 164: Work through: 165: Tim Bray reacting to James Clark, 166: Tim Bray on his own, 167: Eve Maler, 168: 169: NOT DONE YET: 170: change binary / text to unparsed / parsed. 171: handle James's suggestion about < in attriubte values 172: uppercase hex characters, 173: namechar list, 174: </sitem> 175: <sitem>1997-12-01 : JB : add some column-width parameters</sitem> 176: <sitem>1997-12-01 : CMSMcQ : begin round of changes to incorporate 177: recent WG decisions and other corrections: 178: binding sources of character encoding info (27 Aug / 3 Sept), 179: correct wording of Faust quotation (restore dropped line), 180: drop SDD from EncodingDecl, 181: change text at version number 1.0, 182: drop misleading (wrong!) sentence about ignorables and extenders, 183: modify definition of PCData to make bar on msc grammatical, 184: change grammar's handling of internal subset (drop non-terminal markupdecls), 185: change definition of includeSect to allow conditional sections, 186: add integral-declaration constraint on internal subset, 187: drop misleading / dangerous sentence about relationship of 188: entities with system storage objects, 189: change table body tag to htbody as per EM change to DTD, 190: add rule about space normalization in public identifiers, 191: add description of how to generate our name-space rules from 192: Unicode character database (needs further work!). 193: </sitem> 194: <sitem>1997-10-08 : TB : Removed %-constructs again, new rules 195: for PE appearance.</sitem> 196: <sitem>1997-10-01 : TB : Case-sensitive markup; cleaned up 197: element-type defs, lotsa little edits for style</sitem> 198: <sitem>1997-09-25 : TB : Change to elm's new DTD, with 199: substantial detail cleanup as a side-effect</sitem> 200: <sitem>1997-07-24 : CMSMcQ : correct error (lost *) in definition 201: of ignoreSectContents (thanks to Makoto Murata)</sitem> 202: <sitem>Allow all empty elements to have end-tags, consistent with 203: SGML TC (as per JJC).</sitem> 204: <sitem>1997-07-23 : CMSMcQ : pre-emptive strike on pending corrections: 205: introduce the term 'empty-element tag', note that all empty elements 206: may use it, and elements declared EMPTY must use it. 207: Add WFC requiring encoding decl to come first in an entity. 208: Redefine notations to point to PIs as well as binary entities. 209: Change autodetection table by removing bytes 3 and 4 from 210: examples with Byte Order Mark. 211: Add content model as a term and clarify that it applies to both 212: mixed and element content. 213: </sitem> 214: <sitem>1997-06-30 : CMSMcQ : change date, some cosmetic changes, 215: changes to productions for choice, seq, Mixed, NotationType, 216: Enumeration. Follow James Clark's suggestion and prohibit 217: conditional sections in internal subset. TO DO: simplify 218: production for ignored sections as a result, since we don't 219: need to worry about parsers which don't expand PErefs finding 220: a conditional section.</sitem> 221: <sitem>1997-06-29 : TB : various edits</sitem> 222: <sitem>1997-06-29 : CMSMcQ : further changes: 223: Suppress old FINAL EDIT comments and some dead material. 224: Revise occurrences of % in grammar to exploit Henry Thompson's pun, 225: especially markupdecl and attdef. 226: Remove RMD requirement relating to element content (?). 227: </sitem> 228: <sitem>1997-06-28 : CMSMcQ : Various changes for 1 July draft: 229: Add text for draconian error handling (introduce 230: the term Fatal Error). 231: RE deleta est (changing wording from 232: original announcement to restrict the requirement to validating 233: parsers). 234: Tag definition of validating processor and link to it. 235: Add colon as name character. 236: Change def of %operator. 237: Change standard definitions of lt, gt, amp. 238: Strip leading zeros from #x00nn forms.</sitem> 239: <sitem>1997-04-02 : CMSMcQ : final corrections of editorial errors 240: found in last night's proofreading. Reverse course once more on 241: well-formed: Webster's Second hyphenates it, and that's enough 242: for me.</sitem> 243: <sitem>1997-04-01 : CMSMcQ : corrections from JJC, EM, HT, and self</sitem> 244: <sitem>1997-03-31 : Tim Bray : many changes</sitem> 245: <sitem>1997-03-29 : CMSMcQ : some Henry Thompson (on entity handling), 246: some Charles Goldfarb, some ERB decisions (PE handling in miscellaneous 247: declarations. Changed Ident element to accept def attribute. 248: Allow normalization of Unicode characters. move def of systemliteral 249: into section on literals.</sitem> 250: <sitem>1997-03-28 : CMSMcQ : make as many corrections as possible, from 251: Terry Allen, Norbert Mikula, James Clark, Jon Bosak, Henry Thompson, 252: Paul Grosso, and self. Among other things: give in on "well formed" 253: (Terry is right), tentatively rename QuotedCData as AttValue 254: and Literal as EntityValue to be more informative, since attribute 255: values are the <emph>only</emph> place QuotedCData was used, and 256: vice versa for entity text and Literal. (I'd call it Entity Text, 257: but 8879 uses that name for both internal and external entities.)</sitem> 258: <sitem>1997-03-26 : CMSMcQ : resynch the two forks of this draft, reapply 259: my changes dated 03-20 and 03-21. Normalize old 'may not' to 'must not' 260: except in the one case where it meant 'may or may not'.</sitem> 261: <sitem>1997-03-21 : TB : massive changes on plane flight from Chicago 262: to Vancouver</sitem> 263: <sitem>1997-03-21 : CMSMcQ : correct as many reported errors as possible. 264: </sitem> 265: <sitem>1997-03-20 : CMSMcQ : correct typos listed in CMSMcQ hand copy of spec.</sitem> 266: <sitem>1997-03-20 : CMSMcQ : cosmetic changes preparatory to revision for 267: WWW conference April 1997: restore some of the internal entity 268: references (e.g. to docdate, etc.), change character xA0 to &nbsp; 269: and define nbsp as &#160;, and refill a lot of paragraphs for 270: legibility.</sitem> 271: <sitem>1996-11-12 : CMSMcQ : revise using Tim's edits: 272: Add list type of NUMBERED and change most lists either to 273: BULLETS or to NUMBERED. 274: Suppress QuotedNames, Names (not used). 275: Correct trivial-grammar doc type decl. 276: Rename 'marked section' as 'CDATA section' passim. 277: Also edits from James Clark: 278: Define the set of characters from which [^abc] subtracts. 279: Charref should use just [0-9] not Digit. 280: Location info needs cleaner treatment: remove? (ERB 281: question). 282: One example of a PI has wrong pic. 283: Clarify discussion of encoding names. 284: Encoding failure should lead to unspecified results; don't 285: prescribe error recovery. 286: Don't require exposure of entity boundaries. 287: Ignore white space in element content. 288: Reserve entity names of the form u-NNNN. 289: Clarify relative URLs. 290: And some of my own: 291: Correct productions for content model: model cannot 292: consist of a name, so "elements ::= cp" is no good. 293: </sitem> 294: <sitem>1996-11-11 : CMSMcQ : revise for style. 295: Add new rhs to entity declaration, for parameter entities.</sitem> 296: <sitem>1996-11-10 : CMSMcQ : revise for style. 297: Fix / complete section on names, characters. 298: Add sections on parameter entities, conditional sections. 299: Still to do: Add compatibility note on deterministic content models. 300: Finish stylistic revision.</sitem> 301: <sitem>1996-10-31 : TB : Add Entity Handling section</sitem> 302: <sitem>1996-10-30 : TB : Clean up term & termdef. Slip in 303: ERB decision re EMPTY.</sitem> 304: <sitem>1996-10-28 : TB : Change DTD. Implement some of Michael's 305: suggestions. Change comments back to //. Introduce language for 306: XML namespace reservation. Add section on white-space handling. 307: Lots more cleanup.</sitem> 308: <sitem>1996-10-24 : CMSMcQ : quick tweaks, implement some ERB 309: decisions. Characters are not integers. Comments are /* */ not //. 310: Add bibliographic refs to 10646, HyTime, Unicode. 311: Rename old Cdata as MsData since it's <emph>only</emph> seen 312: in marked sections. Call them attribute-value pairs not 313: name-value pairs, except once. Internal subset is optional, needs 314: '?'. Implied attributes should be signaled to the app, not 315: have values supplied by processor.</sitem> 316: <sitem>1996-10-16 : TB : track down & excise all DSD references; 317: introduce some EBNF for entity declarations.</sitem> 318: <sitem>1996-10-?? : TB : consistency check, fix up scraps so 319: they all parse, get formatter working, correct a few productions.</sitem> 320: <sitem>1996-10-10/11 : CMSMcQ : various maintenance, stylistic, and 321: organizational changes: 322: Replace a few literals with xmlpio and 323: pic entities, to make them consistent and ensure we can change pic 324: reliably when the ERB votes. 325: Drop paragraph on recognizers from notation section. 326: Add match, exact match to terminology. 327: Move old 2.2 XML Processors and Apps into intro. 328: Mention comments, PIs, and marked sections in discussion of 329: delimiter escaping. 330: Streamline discussion of doctype decl syntax. 331: Drop old section of 'PI syntax' for doctype decl, and add 332: section on partial-DTD summary PIs to end of Logical Structures 333: section. 334: Revise DSD syntax section to use Tim's subset-in-a-PI 335: mechanism.</sitem> 336: <sitem>1996-10-10 : TB : eliminate name recognizers (and more?)</sitem> 337: <sitem>1996-10-09 : CMSMcQ : revise for style, consistency through 2.3 338: (Characters)</sitem> 339: <sitem>1996-10-09 : CMSMcQ : re-unite everything for convenience, 340: at least temporarily, and revise quickly</sitem> 341: <sitem>1996-10-08 : TB : first major homogenization pass</sitem> 342: <sitem>1996-10-08 : TB : turn "current" attribute on div type into 343: CDATA</sitem> 344: <sitem>1996-10-02 : TB : remould into skeleton + entities</sitem> 345: <sitem>1996-09-30 : CMSMcQ : add a few more sections prior to exchange 346: with Tim.</sitem> 347: <sitem>1996-09-20 : CMSMcQ : finish transcribing notes.</sitem> 348: <sitem>1996-09-19 : CMSMcQ : begin transcribing notes for draft.</sitem> 349: <sitem>1996-09-13 : CMSMcQ : made outline from notes of 09-06, 350: do some housekeeping</sitem> 351: </slist> 352: </revisiondesc> 353: </header> 354: <body> 355: <div1 id="sec-intro"> 356: <head>Introduction</head> 357: Extensible Markup Language, abbreviated XML, describes a class of 358: data objects called <termref def="dt-xml-doc">XML documents</termref> and 359: partially describes the behavior of 360: computer programs which process them. XML is an application profile or 361: restricted form of SGML, the Standard Generalized Markup 362: Language <bibref ref="ISO8879"/>. 363: By construction, XML documents 364: are conforming SGML documents. 365: 366: XML documents are made up of storage units called <termref def="dt-entity">entities</termref>, which contain either parsed 367: or unparsed data. 368: Parsed data is made up of <termref def="dt-character">characters</termref>, 369: some 370: of which form <termref def="dt-chardata">character data</termref>, 371: and some of which form <termref def="dt-markup">markup</termref>. 372: Markup encodes a description of the document's storage layout and 373: logical structure. XML provides a mechanism to impose constraints on 374: the storage layout and logical structure. 375: <termdef id="dt-xml-proc" term="XML Processor">A software module 376: called an <term>XML processor</term> is used to read XML documents 377: and provide access to their content and structure.</termdef> <termdef id="dt-app" term="Application">It is assumed that an XML processor is 378: doing its work on behalf of another module, called the 379: <term>application</term>.</termdef> This specification describes the 380: required behavior of an XML processor in terms of how it must read XML 381: data and the information it must provide to the application. 382: 383: <div2 id="sec-origin-goals"> 384: <head>Origin and Goals</head> 385: XML was developed by an XML Working Group (originally known as the 386: SGML Editorial Review Board) formed under the auspices of the World 387: Wide Web Consortium (W3C) in 1996. 388: It was chaired by Jon Bosak of Sun 389: Microsystems with the active participation of an XML Special 390: Interest Group (previously known as the SGML Working Group) also 391: organized by the W3C. The membership of the XML Working Group is given 392: in an appendix. Dan Connolly served as the WG's contact with the W3C. 393: 394: The design goals for XML are:<olist> 395: <item>XML shall be straightforwardly usable over the 396: Internet.</item> 397: <item>XML shall support a wide variety of applications.</item> 398: <item>XML shall be compatible with SGML.</item> 399: <item>It shall be easy to write programs which process XML 400: documents.</item> 401: <item>The number of optional features in XML is to be kept to the 402: absolute minimum, ideally zero.</item> 403: <item>XML documents should be human-legible and reasonably 404: clear.</item> 405: <item>The XML design should be prepared quickly.</item> 406: <item>The design of XML shall be formal and concise.</item> 407: <item>XML documents shall be easy to create.</item> 408: <item>Terseness in XML markup is of minimal importance.</item></olist> 409: 410: This specification, 411: together with associated standards 412: (Unicode and ISO/IEC 10646 for characters, 413: Internet RFC 1766 for language identification tags, 414: ISO 639 for language name codes, and 415: ISO 3166 for country name codes), 416: provides all the information necessary to understand 417: XML Version &XML.version; 418: and construct computer programs to process it. 419: This version of the XML specification 420:  421: &doc.distribution;. 422: 423: </div2> 424: 425: 426: 427: 428: <div2 id="sec-terminology"> 429: <head>Terminology</head> 430: 431: The terminology used to describe XML documents is defined in the body of 432: this specification. 433: The terms defined in the following list are used in building those 434: definitions and in describing the actions of an XML processor: 435: <glist> 436: <gitem> 437: <label>may</label> 438: <def><termdef id="dt-may" term="May">Conforming documents and XML 439: processors are permitted to but need not behave as 440: described.</termdef></def> 441: </gitem> 442: <gitem> 443: <label>must</label> 444: <def>Conforming documents and XML processors 445: are required to behave as described; otherwise they are in error. 446:  448: </def> 449: </gitem> 450: <gitem> 451: <label>error</label> 452: <def><termdef id="dt-error" term="Error">A violation of the rules of this 453: specification; results are 454: undefined. Conforming software may detect and report an error and may 455: recover from it.</termdef></def> 456: </gitem> 457: <gitem> 458: <label>fatal error</label> 459: <def><termdef id="dt-fatal" term="Fatal Error">An error 460: which a conforming <termref def="dt-xml-proc">XML processor</termref> 461: must detect and report to the application. 462: After encountering a fatal error, the 463: processor may continue 464: processing the data to search for further errors and may report such 465: errors to the application. In order to support correction of errors, 466: the processor may make unprocessed data from the document (with 467: intermingled character data and markup) available to the application. 468: Once a fatal error is detected, however, the processor must not 469: continue normal processing (i.e., it must not 470: continue to pass character data and information about the document's 471: logical structure to the application in the normal way). 472: </termdef></def> 473: </gitem> 474: <gitem> 475: <label>at user option</label> 476: <def>Conforming software may or must (depending on the modal verb in the 477: sentence) behave as described; if it does, it must 478: provide users a means to enable or disable the behavior 479: described.</def> 480: </gitem> 481: <gitem> 482: <label>validity constraint</label> 483: <def>A rule which applies to all 484: <termref def="dt-valid">valid</termref> XML documents. 485: Violations of validity constraints are errors; they must, at user option, 486: be reported by 487: <termref def="dt-validating">validating XML processors</termref>.</def> 488: </gitem> 489: <gitem> 490: <label>well-formedness constraint</label> 491: <def>A rule which applies to all <termref def="dt-wellformed">well-formed</termref> XML documents. 492: Violations of well-formedness constraints are 493: <termref def="dt-fatal">fatal errors</termref>.</def> 494: </gitem> 495: 496: <gitem> 497: <label>match</label> 498: <def><termdef id="dt-match" term="match">(Of strings or names:) 499: Two strings or names being compared must be identical. 500: Characters with multiple possible representations in ISO/IEC 10646 (e.g. 501: characters with 502: both precomposed and base+diacritic forms) match only if they have the 503: same representation in both strings. 504: At user option, processors may normalize such characters to 505: some canonical form. 506: No case folding is performed. 507: (Of strings and rules in the grammar:) 508: A string matches a grammatical production if it belongs to the 509: language generated by that production. 510: (Of content and content models:) 511: An element matches its declaration when it conforms 512: in the fashion described in the constraint 513: <specref ref="elementvalid"/>. 514: </termdef> 515: </def> 516: </gitem> 517: <gitem> 518: <label>for compatibility</label> 519: <def><termdef id="dt-compat" term="For Compatibility">A feature of 520: XML included solely to ensure that XML remains compatible with SGML. 521: </termdef></def> 522: </gitem> 523: <gitem> 524: <label>for interoperability</label> 525: <def><termdef id="dt-interop" term="For interoperability">A 526: non-binding recommendation included to increase the chances that XML 527: documents can be processed by the existing installed base of SGML 528: processors which predate the 529: &WebSGML;.</termdef></def> 530: </gitem> 531: </glist> 532: 533: </div2> 534: 535: 536: </div1> 537:  538: 539: <div1 id="sec-documents"> 540: <head>Documents</head> 541: 542: <termdef id="dt-xml-doc" term="XML Document"> 543: A data object is an 544: <term>XML document</term> if it is 545: <termref def="dt-wellformed">well-formed</termref>, as 546: defined in this specification. 547: A well-formed XML document may in addition be 548: <termref def="dt-valid">valid</termref> if it meets certain further 549: constraints.</termdef> 550: 551: Each XML document has both a logical and a physical structure. 552: Physically, the document is composed of units called <termref def="dt-entity">entities</termref>. An entity may <termref def="dt-entref">refer</termref> to other entities to cause their 553: inclusion in the document. A document begins in a "root" or <termref def="dt-docent">document entity</termref>. 554: Logically, the document is composed of declarations, elements, 555: comments, 556: character references, and 557: processing 558: instructions, all of which are indicated in the document by explicit 559: markup. 560: The logical and physical structures must nest properly, as described 561: in <specref ref="wf-entities"/>. 562: 563: 564: <div2 id="sec-well-formed"> 565: <head>Well-Formed XML Documents</head> 566: 567: <termdef id="dt-wellformed" term="Well-Formed"> 568: A textual object is 569: a well-formed XML document if:</termdef> 570: <olist> 571: <item>Taken as a whole, it 572: matches the production labeled <nt def="NT-document">document</nt>.</item> 573: <item>It 574: meets all the well-formedness constraints given in this specification. 575: </item> 576: <item>Each of the <termref def="dt-parsedent">parsed entities</termref> 577: which is referenced directly or indirectly within the document is 578: <titleref href="wf-entities">well-formed</titleref>.</item> 579: </olist> 580: 581: <scrap lang="ebnf" id="document"> 582: <head>Document</head> 583: <prod id="NT-document"><lhs>document</lhs> 584: <rhs><nt def="NT-prolog">prolog</nt> 585: <nt def="NT-element">element</nt> 586: <nt def="NT-Misc">Misc</nt>*</rhs></prod> 587: </scrap> 588: 589: Matching the <nt def="NT-document">document</nt> production 590: implies that: 591: <olist> 592: <item>It contains one or more 593: <termref def="dt-element">elements</termref>. 594: </item> 595:  603: <item><termdef id="dt-root" term="Root Element">There is exactly 604: one element, called the <term>root</term>, or document element, no 605: part of which appears in the <termref def="dt-content">content</termref> of any other element.</termdef> 606: For all other elements, if the start-tag is in the content of another 607: element, the end-tag is in the content of the same element. More 608: simply stated, the elements, delimited by start- and end-tags, nest 609: properly within each other. 610: </item> 611: </olist> 612: 613: <termdef id="dt-parentchild" term="Parent/Child">As a consequence 614: of this, 615: for each non-root element 616: <code>C</code> in the document, there is one other element <code>P</code> 617: in the document such that 618: <code>C</code> is in the content of <code>P</code>, but is not in 619: the content of any other element that is in the content of 620: <code>P</code>. 621: <code>P</code> is referred to as the 622: <term>parent</term> of <code>C</code>, and <code>C</code> as a 623: <term>child</term> of <code>P</code>.</termdef></div2> 624: 625: <div2 id="charsets"> 626: <head>Characters</head> 627: 628: <termdef id="dt-text" term="Text">A parsed entity contains 629: <term>text</term>, a sequence of 630: <termref def="dt-character">characters</termref>, 631: which may represent markup or character data.</termdef> 632: <termdef id="dt-character" term="Character">A <term>character</term> 633: is an atomic unit of text as specified by 634: ISO/IEC 10646 <bibref ref="ISO10646"/>. 635: Legal characters are tab, carriage return, line feed, and the legal 636: graphic characters of Unicode and ISO/IEC 10646. 637: The use of "compatibility characters", as defined in section 6.8 638: of <bibref ref="Unicode"/>, is discouraged. 639: </termdef> 640: <scrap lang="ebnf" id="char32"> 641: <head>Character Range</head> 642: <prodgroup pcw2="4" pcw4="17.5" pcw5="11"> 643: <prod id="NT-Char"><lhs>Char</lhs> 644: <rhs>#x9 | #xA | #xD | [#x20-#xD7FF] | [#xE000-#xFFFD] 645: | [#x10000-#x10FFFF]</rhs> 646: <com>any Unicode character, excluding the 647: surrogate blocks, FFFE, and FFFF.</com> </prod> 648: </prodgroup> 649: </scrap> 650: 651: 652: The mechanism for encoding character code points into bit patterns may 653: vary from entity to entity. All XML processors must accept the UTF-8 654: and UTF-16 encodings of 10646; the mechanisms for signaling which of 655: the two is in use, or for bringing other encodings into play, are 656: discussed later, in <specref ref="charencoding"/>. 657: 658:  664: </div2> 665: 666: <div2 id="sec-common-syn"> 667: <head>Common Syntactic Constructs</head> 668: 669: This section defines some symbols used widely in the grammar. 670: <nt def="NT-S">S</nt> (white space) consists of one or more space (#x20) 671: characters, carriage returns, line feeds, or tabs. 672: 673: <scrap lang="ebnf" id="white"> 674: <head>White Space</head> 675: <prodgroup pcw2="4" pcw4="17.5" pcw5="11"> 676: <prod id="NT-S"><lhs>S</lhs> 677: <rhs>(#x20 | #x9 | #xD | #xA)+</rhs> 678: </prod> 679: </prodgroup> 680: </scrap> 681: Characters are classified for convenience as letters, digits, or other 682: characters. Letters consist of an alphabetic or syllabic 683: base character possibly 684: followed by one or more combining characters, or of an ideographic 685: character. 686: Full definitions of the specific characters in each class 687: are given in <specref ref="CharClasses"/>. 688: <termdef id="dt-name" term="Name">A <term>Name</term> is a token 689: beginning with a letter or one of a few punctuation characters, and continuing 690: with letters, digits, hyphens, underscores, colons, or full stops, together 691: known as name characters.</termdef> 692: Names beginning with the string "<code>xml</code>", or any string 693: which would match <code>(('X'|'x') ('M'|'m') ('L'|'l'))</code>, are 694: reserved for standardization in this or future versions of this 695: specification. 696: 697: <note> 698: The colon character within XML names is reserved for experimentation with 699: name spaces. 700: Its meaning is expected to be 701: standardized at some future point, at which point those documents 702: using the colon for experimental purposes may need to be updated. 703: (There is no guarantee that any name-space mechanism 704: adopted for XML will in fact use the colon as a name-space delimiter.) 705: In practice, this means that authors should not use the colon in XML 706: names except as part of name-space experiments, but that XML processors 707: should accept the colon as a name character. 708: </note> 709: An 710: <nt def="NT-Nmtoken">Nmtoken</nt> (name token) is any mixture of 711: name characters. 712: <scrap lang="ebnf"> 713: <head>Names and Tokens</head> 714: <prod id="NT-NameChar"><lhs>NameChar</lhs> 715: <rhs><nt def="NT-Letter">Letter</nt> 716: | <nt def="NT-Digit">Digit</nt> 717: | '.' | '-' | '_' | ':' 718: | <nt def="NT-CombiningChar">CombiningChar</nt> 719: | <nt def="NT-Extender">Extender</nt></rhs> 720: </prod> 721: <prod id="NT-Name"><lhs>Name</lhs> 722: <rhs>(<nt def="NT-Letter">Letter</nt> | '_' | ':') 723: (<nt def="NT-NameChar">NameChar</nt>)*</rhs></prod> 724: <prod id="NT-Names"><lhs>Names</lhs> 725: <rhs><nt def="NT-Name">Name</nt> 726: (<nt def="NT-S">S</nt> <nt def="NT-Name">Name</nt>)*</rhs></prod> 727: <prod id="NT-Nmtoken"><lhs>Nmtoken</lhs> 728: <rhs>(<nt def="NT-NameChar">NameChar</nt>)+</rhs></prod> 729: <prod id="NT-Nmtokens"><lhs>Nmtokens</lhs> 730: <rhs><nt def="NT-Nmtoken">Nmtoken</nt> (<nt def="NT-S">S</nt> <nt def="NT-Nmtoken">Nmtoken</nt>)*</rhs></prod> 731: </scrap> 732: 733: Literal data is any quoted string not containing 734: the quotation mark used as a delimiter for that string. 735: Literals are used 736: for specifying the content of internal entities 737: (<nt def="NT-EntityValue">EntityValue</nt>), 738: the values of attributes (<nt def="NT-AttValue">AttValue</nt>), 739: and external identifiers 740: (<nt def="NT-SystemLiteral">SystemLiteral</nt>). 741: Note that a <nt def="NT-SystemLiteral">SystemLiteral</nt> 742: can be parsed without scanning for markup. 743: <scrap lang="ebnf"> 744: <head>Literals</head> 745: <prod id="NT-EntityValue"><lhs>EntityValue</lhs> 746: <rhs>'"' 747: ([^%&"] 748: | <nt def="NT-PEReference">PEReference</nt> 749: | <nt def="NT-Reference">Reference</nt>)* 750: '"' 751: </rhs> 752: <rhs>|  753: "'" 754: ([^%&'] 755: | <nt def="NT-PEReference">PEReference</nt> 756: | <nt def="NT-Reference">Reference</nt>)* 757: "'"</rhs> 758: </prod> 759: <prod id="NT-AttValue"><lhs>AttValue</lhs> 760: <rhs>'"' 761: ([^<&"] 762: | <nt def="NT-Reference">Reference</nt>)* 763: '"' 764: </rhs> 765: <rhs>|  766: "'" 767: ([^<&'] 768: | <nt def="NT-Reference">Reference</nt>)* 769: "'"</rhs> 770: </prod> 771: <prod id="NT-SystemLiteral"><lhs>SystemLiteral</lhs> 772: <rhs>('"' [^"]* '"') | ("'" [^']* "'") 773: </rhs> 774: </prod> 775: <prod id="NT-PubidLiteral"><lhs>PubidLiteral</lhs> 776: <rhs>'"' <nt def="NT-PubidChar">PubidChar</nt>* 777: '"' 778: | "'" (<nt def="NT-PubidChar">PubidChar</nt> - "'")* "'"</rhs> 779: </prod> 780: <prod id="NT-PubidChar"><lhs>PubidChar</lhs> 781: <rhs>#x20 | #xD | #xA 782: | [a-zA-Z0-9] 783: | [-'()+,./:=?;!*#@$_%]</rhs> 784: </prod> 785: </scrap> 786: 787: 788: </div2> 789: 790: <div2 id="syntax"> 791: <head>Character Data and Markup</head> 792: 793: <termref def="dt-text">Text</termref> consists of intermingled 794: <termref def="dt-chardata">character 795: data</termref> and markup. 796: <termdef id="dt-markup" term="Markup"><term>Markup</term> takes the form of 797: <termref def="dt-stag">start-tags</termref>, 798: <termref def="dt-etag">end-tags</termref>, 799: <termref def="dt-empty">empty-element tags</termref>, 800: <termref def="dt-entref">entity references</termref>, 801: <termref def="dt-charref">character references</termref>, 802: <termref def="dt-comment">comments</termref>, 803: <termref def="dt-cdsection">CDATA section</termref> delimiters, 804: <termref def="dt-doctype">document type declarations</termref>, and 805: <termref def="dt-pi">processing instructions</termref>. 806: </termdef> 807: 808: <termdef id="dt-chardata" term="Character Data">All text that is not markup 809: constitutes the <term>character data</term> of 810: the document.</termdef> 811: The ampersand character (&) and the left angle bracket (<) 812: may appear in their literal form <emph>only</emph> when used as markup 813: delimiters, or within a <termref def="dt-comment">comment</termref>, a 814: <termref def="dt-pi">processing instruction</termref>, 815: or a <termref def="dt-cdsection">CDATA section</termref>. 816: 817: They are also legal within the <termref def="dt-litentval">literal entity 818: value</termref> of an internal entity declaration; see 819: <specref ref="wf-entities"/>. 820:  821: If they are needed elsewhere, 822: they must be <termref def="dt-escape">escaped</termref> 823: using either <termref def="dt-charref">numeric character references</termref> 824: or the strings 825: "<code>&amp;</code>" and "<code>&lt;</code>" respectively. 826: The right angle 827: bracket (>) may be represented using the string 828: "<code>&gt;</code>", and must, <termref def="dt-compat">for 829: compatibility</termref>, 830: be escaped using 831: "<code>&gt;</code>" or a character reference 832: when it appears in the string 833: "<code>]]></code>" 834: in content, 835: when that string is not marking the end of 836: a <termref def="dt-cdsection">CDATA section</termref>. 837: 838: 839: In the content of elements, character data 840: is any string of characters which does 841: not contain the start-delimiter of any markup. 842: In a CDATA section, character data 843: is any string of characters not including the CDATA-section-close 844: delimiter, "<code>]]></code>". 845: 846: To allow attribute values to contain both single and double quotes, the 847: apostrophe or single-quote character (') may be represented as 848: "<code>&apos;</code>", and the double-quote character (") as 849: "<code>&quot;</code>". 850: <scrap lang="ebnf"> 851: <head>Character Data</head> 852: <prod id="NT-CharData"> 853: <lhs>CharData</lhs> 854: <rhs>[^<&]* - ([^<&]* ']]>' [^<&]*)</rhs> 855: </prod> 856: </scrap> 857: 858: </div2> 859: 860: <div2 id="sec-comments"> 861: <head>Comments</head> 862: 863: <termdef id="dt-comment" term="Comment"><term>Comments</term> may 864: appear anywhere in a document outside other 865: <termref def="dt-markup">markup</termref>; in addition, 866: they may appear within the document type declaration 867: at places allowed by the grammar. 868: They are not part of the document's <termref def="dt-chardata">character 869: data</termref>; an XML 870: processor may, but need not, make it possible for an application to 871: retrieve the text of comments. 872: <termref def="dt-compat">For compatibility</termref>, the string 873: "<code>--</code>" (double-hyphen) must not occur within 874: comments. 875: <scrap lang="ebnf"> 876: <head>Comments</head> 877: <prod id="NT-Comment"><lhs>Comment</lhs> 878: <rhs>''</rhs> 882: </prod> 883: </scrap> 884: </termdef> 885: An example of a comment: 886: <eg><!&como; declarations for <head> & <body> &comc;></eg> 887: 888: </div2> 889: 890: <div2 id="sec-pi"> 891: <head>Processing Instructions</head> 892: 893: <termdef id="dt-pi" term="Processing instruction"><term>Processing 894: instructions</term> (PIs) allow documents to contain instructions 895: for applications. 896: 897: <scrap lang="ebnf"> 898: <head>Processing Instructions</head> 899: <prod id="NT-PI"><lhs>PI</lhs> 900: <rhs>'<?' <nt def="NT-PITarget">PITarget</nt> 901: (<nt def="NT-S">S</nt> 902: (<nt def="NT-Char">Char</nt>* - 903: (<nt def="NT-Char">Char</nt>* &pic; <nt def="NT-Char">Char</nt>*)))? 904: &pic;</rhs></prod> 905: <prod id="NT-PITarget"><lhs>PITarget</lhs> 906: <rhs><nt def="NT-Name">Name</nt> - 907: (('X' | 'x') ('M' | 'm') ('L' | 'l'))</rhs> 908: </prod> 909: </scrap></termdef> 910: PIs are not part of the document's <termref def="dt-chardata">character 911: data</termref>, but must be passed through to the application. The 912: PI begins with a target (<nt def="NT-PITarget">PITarget</nt>) used 913: to identify the application to which the instruction is directed. 914: The target names "<code>XML</code>", "<code>xml</code>", and so on are 915: reserved for standardization in this or future versions of this 916: specification. 917: The 918: XML <termref def="dt-notation">Notation</termref> mechanism 919: may be used for 920: formal declaration of PI targets. 921: 922: </div2> 923: 924: <div2 id="sec-cdata-sect"> 925: <head>CDATA Sections</head> 926: 927: <termdef id="dt-cdsection" term="CDATA Section"><term>CDATA sections</term> 928: may occur 929: anywhere character data may occur; they are 930: used to escape blocks of text containing characters which would 931: otherwise be recognized as markup. CDATA sections begin with the 932: string "<code><![CDATA[</code>" and end with the string 933: "<code>]]></code>": 934: <scrap lang="ebnf"> 935: <head>CDATA Sections</head> 936: <prod id="NT-CDSect"><lhs>CDSect</lhs> 937: <rhs><nt def="NT-CDStart">CDStart</nt> 938: <nt def="NT-CData">CData</nt> 939: <nt def="NT-CDEnd">CDEnd</nt></rhs></prod> 940: <prod id="NT-CDStart"><lhs>CDStart</lhs> 941: <rhs>'<![CDATA['</rhs> 942: </prod> 943: <prod id="NT-CData"><lhs>CData</lhs> 944: <rhs>(<nt def="NT-Char">Char</nt>* - 945: (<nt def="NT-Char">Char</nt>* ']]>' <nt def="NT-Char">Char</nt>*)) 946: </rhs> 947: </prod> 948: <prod id="NT-CDEnd"><lhs>CDEnd</lhs> 949: <rhs>']]>'</rhs> 950: </prod> 951: </scrap> 952: 953: Within a CDATA section, only the <nt def="NT-CDEnd">CDEnd</nt> string is 954: recognized as markup, so that left angle brackets and ampersands may occur in 955: their literal form; they need not (and cannot) be escaped using 956: "<code>&lt;</code>" and "<code>&amp;</code>". CDATA sections 957: cannot nest.</termdef> 958: 959: 960: An example of a CDATA section, in which "<code><greeting></code>" and 961: "<code></greeting></code>" 962: are recognized as <termref def="dt-chardata">character data</termref>, not 963: <termref def="dt-markup">markup</termref>: 964: <eg><![CDATA[<greeting>Hello, world!</greeting>]]></eg> 965: 966: </div2> 967: 968: <div2 id="sec-prolog-dtd"> 969: <head>Prolog and Document Type Declaration</head> 970: 971: <termdef id="dt-xmldecl" term="XML Declaration">XML documents 972: may, and should, 973: begin with an <term>XML declaration</term> which specifies 974: the version of 975: XML being used.</termdef> 976: For example, the following is a complete XML document, <termref def="dt-wellformed">well-formed</termref> but not 977: <termref def="dt-valid">valid</termref>: 978: <eg><![CDATA[<?xml version="1.0"?> 979: <greeting>Hello, world!</greeting> 980: ]]></eg> 981: and so is this: 982: <eg><![CDATA[<greeting>Hello, world!</greeting> 983: ]]></eg> 984: 985: 986: The version number "<code>1.0</code>" should be used to indicate 987: conformance to this version of this specification; it is an error 988: for a document to use the value "<code>1.0</code>" 989: if it does not conform to this version of this specification. 990: It is the intent 991: of the XML working group to give later versions of this specification 992: numbers other than "<code>1.0</code>", but this intent does not 993: indicate a 994: commitment to produce any future versions of XML, nor if any are produced, to 995: use any particular numbering scheme. 996: Since future versions are not ruled out, this construct is provided 997: as a means to allow the possibility of automatic version recognition, should 998: it become necessary. 999: Processors may signal an error if they receive documents labeled with 1000: versions they do not support. 1001: 1002: The function of the markup in an XML document is to describe its 1003: storage and logical structure and to associate attribute-value pairs 1004: with its logical structures. XML provides a mechanism, the <termref def="dt-doctype">document type declaration</termref>, to define 1005: constraints on the logical structure and to support the use of 1006: predefined storage units. 1007: 1008: <termdef id="dt-valid" term="Validity">An XML document is 1009: <term>valid</term> if it has an associated document type 1010: declaration and if the document 1011: complies with the constraints expressed in it.</termdef> 1012: The document type declaration must appear before 1013: the first <termref def="dt-element">element</termref> in the document. 1014: <scrap lang="ebnf" id="xmldoc"> 1015: <head>Prolog</head> 1016: <prodgroup pcw2="6" pcw4="17.5" pcw5="9"> 1017: <prod id="NT-prolog"><lhs>prolog</lhs> 1018: <rhs><nt def="NT-XMLDecl">XMLDecl</nt>? 1019: <nt def="NT-Misc">Misc</nt>* 1020: (<nt def="NT-doctypedecl">doctypedecl</nt> 1021: <nt def="NT-Misc">Misc</nt>*)?</rhs></prod> 1022: <prod id="NT-XMLDecl"><lhs>XMLDecl</lhs> 1023: <rhs>&xmlpio; 1024: <nt def="NT-VersionInfo">VersionInfo</nt> 1025: <nt def="NT-EncodingDecl">EncodingDecl</nt>? 1026: <nt def="NT-SDDecl">SDDecl</nt>? 1027: <nt def="NT-S">S</nt>? 1028: &pic;</rhs> 1029: </prod> 1030: <prod id="NT-VersionInfo"><lhs>VersionInfo</lhs> 1031: <rhs><nt def="NT-S">S</nt> 'version' <nt def="NT-Eq">Eq</nt> 1032: (' <nt def="NT-VersionNum">VersionNum</nt> ' 1033: | " <nt def="NT-VersionNum">VersionNum</nt> ")</rhs> 1034: </prod> 1035: <prod id="NT-Eq"><lhs>Eq</lhs> 1036: <rhs><nt def="NT-S">S</nt>? '=' <nt def="NT-S">S</nt>?</rhs></prod> 1037: <prod id="NT-VersionNum"> 1038: <lhs>VersionNum</lhs> 1039: <rhs>([a-zA-Z0-9_.:] | '-')+</rhs> 1040: </prod> 1041: <prod id="NT-Misc"><lhs>Misc</lhs> 1042: <rhs><nt def="NT-Comment">Comment</nt> | <nt def="NT-PI">PI</nt> | 1043: <nt def="NT-S">S</nt></rhs></prod> 1044: </prodgroup> 1045: </scrap> 1046: 1047: <termdef id="dt-doctype" term="Document Type Declaration">The XML 1048: <term>document type declaration</term> 1049: contains or points to 1050: <termref def="dt-markupdecl">markup declarations</termref> 1051: that provide a grammar for a 1052: class of documents. 1053: This grammar is known as a document type definition, 1054: or <term>DTD</term>. 1055: The document type declaration can point to an external subset (a 1056: special kind of 1057: <termref def="dt-extent">external entity</termref>) containing markup 1058: declarations, or can 1059: contain the markup declarations directly in an internal subset, or can do 1060: both. 1061: The DTD for a document consists of both subsets taken 1062: together.</termdef> 1063: 1064: <termdef id="dt-markupdecl" term="markup declaration"> 1065: A <term>markup declaration</term> is 1066: an <termref def="dt-eldecl">element type declaration</termref>, 1067: an <termref def="dt-attdecl">attribute-list declaration</termref>, 1068: an <termref def="dt-entdecl">entity declaration</termref>, or 1069: a <termref def="dt-notdecl">notation declaration</termref>. 1070: </termdef> 1071: These declarations may be contained in whole or in part 1072: within <termref def="dt-PE">parameter entities</termref>, 1073: as described in the well-formedness and validity constraints below. 1074: For fuller information, see 1075: <specref ref="sec-physical-struct"/>. 1076: <scrap lang="ebnf" id="dtd"> 1077: <head>Document Type Definition</head> 1078: <prodgroup pcw2="6" pcw4="17.5" pcw5="9"> 1079: <prod id="NT-doctypedecl"><lhs>doctypedecl</lhs> 1080: <rhs>'<!DOCTYPE' <nt def="NT-S">S</nt> 1081: <nt def="NT-Name">Name</nt> (<nt def="NT-S">S</nt> 1082: <nt def="NT-ExternalID">ExternalID</nt>)? 1083: <nt def="NT-S">S</nt>? ('[' 1084: (<nt def="NT-markupdecl">markupdecl</nt> 1085: | <nt def="NT-PEReference">PEReference</nt> 1086: | <nt def="NT-S">S</nt>)* 1087: ']' 1088: <nt def="NT-S">S</nt>?)? '>'</rhs> 1089: <vc def="vc-roottype"/> 1090: </prod> 1091: <prod id="NT-markupdecl"><lhs>markupdecl</lhs> 1092: <rhs><nt def="NT-elementdecl">elementdecl</nt> 1093: | <nt def="NT-AttlistDecl">AttlistDecl</nt> 1094: | <nt def="NT-EntityDecl">EntityDecl</nt> 1095: | <nt def="NT-NotationDecl">NotationDecl</nt> 1096: | <nt def="NT-PI">PI</nt> 1097: | <nt def="NT-Comment">Comment</nt> 1098: </rhs> 1099: <vc def="vc-PEinMarkupDecl"/> 1100: <wfc def="wfc-PEinInternalSubset"/> 1101: </prod> 1102: 1103: </prodgroup> 1104: </scrap> 1105: 1106: The markup declarations may be made up in whole or in part of 1107: the <termref def="dt-repltext">replacement text</termref> of 1108: <termref def="dt-PE">parameter entities</termref>. 1109: The productions later in this specification for 1110: individual nonterminals (<nt def="NT-elementdecl">elementdecl</nt>, 1111: <nt def="NT-AttlistDecl">AttlistDecl</nt>, and so on) describe 1112: the declarations <emph>after</emph> all the parameter entities have been 1113: <termref def="dt-include">included</termref>. 1114: 1115: <vcnote id="vc-roottype"> 1116: <head>Root Element Type</head> 1117: 1118: The <nt def="NT-Name">Name</nt> in the document type declaration must 1119: match the element type of the <termref def="dt-root">root element</termref>. 1120: 1121: </vcnote> 1122: 1123: <vcnote id="vc-PEinMarkupDecl"> 1124: <head>Proper Declaration/PE Nesting</head> 1125: Parameter-entity 1126: <termref def="dt-repltext">replacement text</termref> must be properly nested 1127: with markup declarations. 1128: That is to say, if either the first character 1129: or the last character of a markup 1130: declaration (<nt def="NT-markupdecl">markupdecl</nt> above) 1131: is contained in the replacement text for a 1132: <termref def="dt-PERef">parameter-entity reference</termref>, 1133: both must be contained in the same replacement text. 1134: </vcnote> 1135: <wfcnote id="wfc-PEinInternalSubset"> 1136: <head>PEs in Internal Subset</head> 1137: In the internal DTD subset, 1138: <termref def="dt-PERef">parameter-entity references</termref> 1139: can occur only where markup declarations can occur, not 1140: within markup declarations. (This does not apply to 1141: references that occur in 1142: external parameter entities or to the external subset.) 1143: 1144: </wfcnote> 1145: 1146: Like the internal subset, the external subset and 1147: any external parameter entities referred to in the DTD 1148: must consist of a series of complete markup declarations of the types 1149: allowed by the non-terminal symbol 1150: <nt def="NT-markupdecl">markupdecl</nt>, interspersed with white space 1151: or <termref def="dt-PERef">parameter-entity references</termref>. 1152: However, portions of the contents 1153: of the 1154: external subset or of external parameter entities may conditionally be ignored 1155: by using 1156: the <termref def="dt-cond-section">conditional section</termref> 1157: construct; this is not allowed in the internal subset. 1158: 1159: <scrap id="ext-Subset"> 1160: <head>External Subset</head> 1161: <prodgroup pcw2="6" pcw4="17.5" pcw5="9"> 1162: <prod id="NT-extSubset"><lhs>extSubset</lhs> 1163: <rhs><nt def="NT-TextDecl">TextDecl</nt>? 1164: <nt def="NT-extSubsetDecl">extSubsetDecl</nt></rhs></prod> 1165: <prod id="NT-extSubsetDecl"><lhs>extSubsetDecl</lhs> 1166: <rhs>( 1167: <nt def="NT-markupdecl">markupdecl</nt> 1168: | <nt def="NT-conditionalSect">conditionalSect</nt> 1169: | <nt def="NT-PEReference">PEReference</nt> 1170: | <nt def="NT-S">S</nt> 1171: )*</rhs> 1172: </prod> 1173: </prodgroup> 1174: </scrap> 1175: The external subset and external parameter entities also differ 1176: from the internal subset in that in them, 1177: <termref def="dt-PERef">parameter-entity references</termref> 1178: are permitted <emph>within</emph> markup declarations, 1179: not only <emph>between</emph> markup declarations. 1180: An example of an XML document with a document type declaration: 1181: <eg><![CDATA[<?xml version="1.0"?> 1182: <!DOCTYPE greeting SYSTEM "hello.dtd"> 1183: <greeting>Hello, world!</greeting> 1184: ]]></eg> 1185: The <termref def="dt-sysid">system identifier</termref> 1186: "<code>hello.dtd</code>" gives the URI of a DTD for the document. 1187: The declarations can also be given locally, as in this 1188: example: 1189: <eg><![CDATA[<?xml version="1.0" encoding="UTF-8" ?> 1190: <!DOCTYPE greeting [ 1191: <!ELEMENT greeting (#PCDATA)> 1192: ]> 1193: <greeting>Hello, world!</greeting> 1194: ]]></eg> 1195: If both the external and internal subsets are used, the 1196: internal subset is considered to occur before the external subset. 1197:  1198: This has the effect that entity and attribute-list declarations in the 1199: internal subset take precedence over those in the external subset. 1200: 1201: </div2> 1202: 1203: <div2 id="sec-rmd"> 1204: <head>Standalone Document Declaration</head> 1205: Markup declarations can affect the content of the document, 1206: as passed from an <termref def="dt-xml-proc">XML processor</termref> 1207: to an application; examples are attribute defaults and entity 1208: declarations. 1209: The standalone document declaration, 1210: which may appear as a component of the XML declaration, signals 1211: whether or not there are such declarations which appear external to 1212: the <termref def="dt-docent">document entity</termref>. 1213: <scrap lang="ebnf" id="fulldtd"> 1214: <head>Standalone Document Declaration</head> 1215: <prodgroup pcw2="4" pcw4="19.5" pcw5="9"> 1216: <prod id="NT-SDDecl"><lhs>SDDecl</lhs> 1217: <rhs> 1218: <nt def="NT-S">S</nt> 1219: 'standalone' <nt def="NT-Eq">Eq</nt> 1220: (("'" ('yes' | 'no') "'") | ('"' ('yes' | 'no') '"')) 1221: </rhs> 1222: <vc def="vc-check-rmd"/></prod> 1223: </prodgroup> 1224: </scrap> 1225: 1226: In a standalone document declaration, the value "<code>yes</code>" indicates 1227: that there 1228: are no markup declarations external to the <termref def="dt-docent">document 1229: entity</termref> (either in the DTD external subset, or in an 1230: external parameter entity referenced from the internal subset) 1231: which affect the information passed from the XML processor to 1232: the application. 1233: The value "<code>no</code>" indicates that there are or may be such 1234: external markup declarations. 1235: Note that the standalone document declaration only 1236: denotes the presence of external <emph>declarations</emph>; the presence, in a 1237: document, of 1238: references to external <emph>entities</emph>, when those entities are 1239: internally declared, 1240: does not change its standalone status. 1241: If there are no external markup declarations, the standalone document 1242: declaration has no meaning. 1243: If there are external markup declarations but there is no standalone 1244: document declaration, the value "<code>no</code>" is assumed. 1245: Any XML document for which <code>standalone="no"</code> holds can 1246: be converted algorithmically to a standalone document, 1247: which may be desirable for some network delivery applications. 1248: <vcnote id="vc-check-rmd"> 1249: <head>Standalone Document Declaration</head> 1250: The standalone document declaration must have 1251: the value "<code>no</code>" if any external markup declarations 1252: contain declarations of:<ulist> 1253: <item>attributes with <termref def="dt-default">default</termref> values, if 1254: elements to which 1255: these attributes apply appear in the document without 1256: specifications of values for these attributes, or</item> 1257: <item>entities (other than &magicents;), 1258: if <termref def="dt-entref">references</termref> to those 1259: entities appear in the document, or 1260: </item> 1261: <item>attributes with values subject to 1262: <titleref href="AVNormalize">normalization</titleref>, where the 1263: attribute appears in the document with a value which will 1264: change as a result of normalization, or 1265: </item> 1266: <item> 1267: element types with <termref def="dt-elemcontent">element content</termref>, 1268: if white space occurs 1269: directly within any instance of those types. 1270: </item> 1271: </ulist> 1272: 1273: </vcnote> 1274: An example XML declaration with a standalone document declaration:<eg><?xml version="&XML.version;" standalone='yes'?></eg> 1275: </div2> 1276: <div2 id="sec-white-space"> 1277: <head>White Space Handling</head> 1278: 1279: In editing XML documents, it is often convenient to use "white space" 1280: (spaces, tabs, and blank lines, denoted by the nonterminal 1281: <nt def="NT-S">S</nt> in this specification) to 1282: set apart the markup for greater readability. Such white space is typically 1283: not intended for inclusion in the delivered version of the document. 1284: On the other hand, "significant" white space that should be preserved in the 1285: delivered version is common, for example in poetry and 1286: source code. 1287: An <termref def="dt-xml-proc">XML processor</termref> 1288: must always pass all characters in a document that are not 1289: markup through to the application. A <termref def="dt-validating"> 1290: validating XML processor</termref> must also inform the application 1291: which of these characters constitute white space appearing 1292: in <termref def="dt-elemcontent">element content</termref>. 1293: 1294: A special <termref def="dt-attr">attribute</termref> 1295: named <kw>xml:space</kw> may be attached to an element 1296: to signal an intention that in that element, 1297: white space should be preserved by applications. 1298: In valid documents, this attribute, like any other, must be 1299: <termref def="dt-attdecl">declared</termref> if it is used. 1300: When declared, it must be given as an 1301: <termref def="dt-enumerated">enumerated type</termref> whose only 1302: possible values are "<code>default</code>" and "<code>preserve</code>". 1303: For example:<eg><![CDATA[ <!ATTLIST poem xml:space (default|preserve) 'preserve'>]]></eg> 1304: The value "<code>default</code>" signals that applications' 1305: default white-space processing modes are acceptable for this element; the 1306: value "<code>preserve</code>" indicates the intent that applications preserve 1307: all the white space. 1308: This declared intent is considered to apply to all elements within the content 1309: of the element where it is specified, unless overriden with another instance 1310: of the <kw>xml:space</kw> attribute. 1311: 1312: The <termref def="dt-root">root element</termref> of any document 1313: is considered to have signaled no intentions as regards application space 1314: handling, unless it provides a value for 1315: this attribute or the attribute is declared with a default value. 1316: 1317: 1318: </div2> 1319: <div2 id="sec-line-ends"> 1320: <head>End-of-Line Handling</head> 1321: XML <termref def="dt-parsedent">parsed entities</termref> are often stored in 1322: computer files which, for editing convenience, are organized into lines. 1323: These lines are typically separated by some combination of the characters 1324: carriage-return (#xD) and line-feed (#xA). 1325: To simplify the tasks of <termref def="dt-app">applications</termref>, 1326: wherever an external parsed entity or the literal entity value 1327: of an internal parsed entity contains either the literal 1328: two-character sequence "#xD#xA" or a standalone literal 1329: #xD, an <termref def="dt-xml-proc">XML processor</termref> must 1330: pass to the application the single character #xA. 1331: (This behavior can 1332: conveniently be produced by normalizing all 1333: line breaks to #xA on input, before parsing.) 1334: 1335: </div2> 1336: <div2 id="sec-lang-tag"> 1337: <head>Language Identification</head> 1338: In document processing, it is often useful to 1339: identify the natural or formal language 1340: in which the content is 1341: written. 1342: A special <termref def="dt-attr">attribute</termref> named 1343: <kw>xml:lang</kw> may be inserted in 1344: documents to specify the 1345: language used in the contents and attribute values 1346: of any element in an XML document. 1347: In valid documents, this attribute, like any other, must be 1348: <termref def="dt-attdecl">declared</termref> if it is used. 1349: The values of the attribute are language identifiers as defined 1350: by <bibref ref="RFC1766"/>, "Tags for the Identification of Languages": 1351: <scrap lang="ebnf"> 1352: <head>Language Identification</head> 1353: <prod id="NT-LanguageID"><lhs>LanguageID</lhs> 1354: <rhs><nt def="NT-Langcode">Langcode</nt> 1355: ('-' <nt def="NT-Subcode">Subcode</nt>)*</rhs></prod> 1356: <prod id="NT-Langcode"><lhs>Langcode</lhs> 1357: <rhs><nt def="NT-ISO639Code">ISO639Code</nt> | 1358: <nt def="NT-IanaCode">IanaCode</nt> | 1359: <nt def="NT-UserCode">UserCode</nt></rhs> 1360: </prod> 1361: <prod id="NT-ISO639Code"><lhs>ISO639Code</lhs> 1362: <rhs>([a-z] | [A-Z]) ([a-z] | [A-Z])</rhs></prod> 1363: <prod id="NT-IanaCode"><lhs>IanaCode</lhs> 1364: <rhs>('i' | 'I') '-' ([a-z] | [A-Z])+</rhs></prod> 1365: <prod id="NT-UserCode"><lhs>UserCode</lhs> 1366: <rhs>('x' | 'X') '-' ([a-z] | [A-Z])+</rhs></prod> 1367: <prod id="NT-Subcode"><lhs>Subcode</lhs> 1368: <rhs>([a-z] | [A-Z])+</rhs></prod> 1369: </scrap> 1370: The <nt def="NT-Langcode">Langcode</nt> may be any of the following: 1371: <ulist> 1372: <item>a two-letter language code as defined by 1373: <bibref ref="ISO639"/>, "Codes 1374: for the representation of names of languages"</item> 1375: <item>a language identifier registered with the Internet 1376: Assigned Numbers Authority <bibref ref="IANA"/>; these begin with the 1377: prefix "<code>i-</code>" (or "<code>I-</code>")</item> 1378: <item>a language identifier assigned by the user, or agreed on 1379: between parties in private use; these must begin with the 1380: prefix "<code>x-</code>" or "<code>X-</code>" in order to ensure that they do not conflict 1381: with names later standardized or registered with IANA</item> 1382: </ulist> 1383: There may be any number of <nt def="NT-Subcode">Subcode</nt> segments; if 1384: the first 1385: subcode segment exists and the Subcode consists of two 1386: letters, then it must be a country code from 1387: <bibref ref="ISO3166"/>, "Codes 1388: for the representation of names of countries." 1389: If the first 1390: subcode consists of more than two letters, it must be 1391: a subcode for the language in question registered with IANA, 1392: unless the <nt def="NT-Langcode">Langcode</nt> begins with the prefix 1393: "<code>x-</code>" or 1394: "<code>X-</code>". 1395: It is customary to give the language code in lower case, and 1396: the country code (if any) in upper case. 1397: Note that these values, unlike other names in XML documents, 1398: are case insensitive. 1399: For example: 1400: <eg><![CDATA[The quick brown fox jumps over the lazy dog. 1401: What colour is it? 1402: What color is it? 1403: <sp who="Faust" desc='leise' xml:lang="de"> 1404: <l>Habe nun, ach! Philosophie,</l> 1405: <l>Juristerei, und Medizin</l> 1406: <l>und leider auch Theologie</l> 1407: <l>durchaus studiert mit heißem Bemüh'n.</l> 1408: </sp>]]></eg> 1409:  1413: The intent declared with <kw>xml:lang</kw> is considered to apply to 1414: all attributes and content of the element where it is specified, 1415: unless overridden with an instance of <kw>xml:lang</kw> 1416: on another element within that content. 1417:  1432: A simple declaration for <kw>xml:lang</kw> might take 1433: the form 1434: <eg>xml:lang NMTOKEN #IMPLIED</eg> 1435: but specific default values may also be given, if appropriate. In a 1436: collection of French poems for English students, with glosses and 1437: notes in English, the xml:lang attribute might be declared this way: 1438: <eg><![CDATA[ <!ATTLIST poem xml:lang NMTOKEN 'fr'> 1439: <!ATTLIST gloss xml:lang NMTOKEN 'en'> 1440: <!ATTLIST note xml:lang NMTOKEN 'en'>]]></eg> 1441: 1442: 1443: </div2> 1444: </div1> 1445:  1446: 1447: <div1 id="sec-logical-struct"> 1448: <head>Logical Structures</head> 1449: 1450: <termdef id="dt-element" term="Element">Each <termref def="dt-xml-doc">XML document</termref> contains one or more 1451: <term>elements</term>, the boundaries of which are 1452: either delimited by <termref def="dt-stag">start-tags</termref> 1453: and <termref def="dt-etag">end-tags</termref>, or, for <termref def="dt-empty">empty</termref> elements, by an <termref def="dt-eetag">empty-element tag</termref>. Each element has a type, 1454: identified by name, sometimes called its "generic 1455: identifier" (GI), and may have a set of 1456: attribute specifications.</termdef> Each attribute specification 1457: has a <termref def="dt-attrname">name</termref> and a <termref def="dt-attrval">value</termref>. 1458: 1459: <scrap lang="ebnf"><head>Element</head> 1460: <prod id="NT-element"><lhs>element</lhs> 1461: <rhs><nt def="NT-EmptyElemTag">EmptyElemTag</nt></rhs> 1462: <rhs>| <nt def="NT-STag">STag</nt> <nt def="NT-content">content</nt> 1463: <nt def="NT-ETag">ETag</nt></rhs> 1464: <wfc def="GIMatch"/> 1465: <vc def="elementvalid"/> 1466: </prod> 1467: </scrap> 1468: This specification does not constrain the semantics, use, or (beyond 1469: syntax) names of the element types and attributes, except that names 1470: beginning with a match to <code>(('X'|'x')('M'|'m')('L'|'l'))</code> 1471: are reserved for standardization in this or future versions of this 1472: specification. 1473: 1474: <wfcnote id="GIMatch"> 1475: <head>Element Type Match</head> 1476: 1477: The <nt def="NT-Name">Name</nt> in an element's end-tag must match 1478: the element type in 1479: the start-tag. 1480: 1481: </wfcnote> 1482: <vcnote id="elementvalid"> 1483: <head>Element Valid</head> 1484: An element is 1485: valid if 1486: there is a declaration matching 1487: <nt def="NT-elementdecl">elementdecl</nt> where the 1488: <nt def="NT-Name">Name</nt> matches the element type, and 1489: one of the following holds: 1490: <olist> 1491: <item>The declaration matches <kw>EMPTY</kw> and the element has no 1492: <termref def="dt-content">content</termref>.</item> 1493: <item>The declaration matches <nt def="NT-children">children</nt> and 1494: the sequence of 1495: <termref def="dt-parentchild">child elements</termref> 1496: belongs to the language generated by the regular expression in 1497: the content model, with optional white space (characters 1498: matching the nonterminal <nt def="NT-S">S</nt>) between each pair 1499: of child elements.</item> 1500: <item>The declaration matches <nt def="NT-Mixed">Mixed</nt> and 1501: the content consists of <termref def="dt-chardata">character 1502: data</termref> and <termref def="dt-parentchild">child elements</termref> 1503: whose types match names in the content model.</item> 1504: <item>The declaration matches <kw>ANY</kw>, and the types 1505: of any <termref def="dt-parentchild">child elements</termref> have 1506: been declared.</item> 1507: </olist> 1508: </vcnote> 1509: 1510: <div2 id="sec-starttags"> 1511: <head>Start-Tags, End-Tags, and Empty-Element Tags</head> 1512: 1513: <termdef id="dt-stag" term="Start-Tag">The beginning of every 1514: non-empty XML element is marked by a <term>start-tag</term>. 1515: <scrap lang="ebnf"> 1516: <head>Start-tag</head> 1517: <prodgroup pcw2="6" pcw4="15" pcw5="11.5"> 1518: <prod id="NT-STag"><lhs>STag</lhs> 1519: <rhs>'<' <nt def="NT-Name">Name</nt> 1520: (<nt def="NT-S">S</nt> <nt def="NT-Attribute">Attribute</nt>)* 1521: <nt def="NT-S">S</nt>? '>'</rhs> 1522: <wfc def="uniqattspec"/> 1523: </prod> 1524: <prod id="NT-Attribute"><lhs>Attribute</lhs> 1525: <rhs><nt def="NT-Name">Name</nt> <nt def="NT-Eq">Eq</nt> 1526: <nt def="NT-AttValue">AttValue</nt></rhs> 1527: <vc def="ValueType"/> 1528: <wfc def="NoExternalRefs"/> 1529: <wfc def="CleanAttrVals"/></prod> 1530: </prodgroup> 1531: </scrap> 1532: The <nt def="NT-Name">Name</nt> in 1533: the start- and end-tags gives the 1534: element's <term>type</term>.</termdef> 1535: <termdef id="dt-attr" term="Attribute"> 1536: The <nt def="NT-Name">Name</nt>-<nt def="NT-AttValue">AttValue</nt> pairs are 1537: referred to as 1538: the <term>attribute specifications</term> of the element</termdef>, 1539: <termdef id="dt-attrname" term="Attribute Name">with the 1540: <nt def="NT-Name">Name</nt> in each pair 1541: referred to as the <term>attribute name</term></termdef> and 1542: <termdef id="dt-attrval" term="Attribute Value">the content of the 1543: <nt def="NT-AttValue">AttValue</nt> (the text between the 1544: <code>'</code> or <code>"</code> delimiters) 1545: as the <term>attribute value</term>.</termdef> 1546: 1547: <wfcnote id="uniqattspec"> 1548: <head>Unique Att Spec</head> 1549: 1550: No attribute name may appear more than once in the same start-tag 1551: or empty-element tag. 1552: 1553: </wfcnote> 1554: <vcnote id="ValueType"> 1555: <head>Attribute Value Type</head> 1556: 1557: The attribute must have been declared; the value must be of the type 1558: declared for it. 1559: (For attribute types, see <specref ref="attdecls"/>.) 1560: 1561: </vcnote> 1562: <wfcnote id="NoExternalRefs"> 1563: <head>No External Entity References</head> 1564: 1565: Attribute values cannot contain direct or indirect entity references 1566: to external entities. 1567: 1568: </wfcnote> 1569: <wfcnote id="CleanAttrVals"> 1570: <head>No <code><</code> in Attribute Values</head> 1571: The <termref def="dt-repltext">replacement text</termref> of any entity 1572: referred to directly or indirectly in an attribute 1573: value (other than "<code>&lt;</code>") must not contain 1574: a <code><</code>. 1575: </wfcnote> 1576: An example of a start-tag: 1577: <eg><termdef id="dt-dog" term="dog"></eg> 1578: <termdef id="dt-etag" term="End Tag">The end of every element 1579: that begins with a start-tag must 1580: be marked by an <term>end-tag</term> 1581: containing a name that echoes the element's type as given in the 1582: start-tag: 1583: <scrap lang="ebnf"> 1584: <head>End-tag</head> 1585: <prodgroup pcw2="6" pcw4="15" pcw5="11.5"> 1586: <prod id="NT-ETag"><lhs>ETag</lhs> 1587: <rhs>'</' <nt def="NT-Name">Name</nt> 1588: <nt def="NT-S">S</nt>? '>'</rhs></prod> 1589: </prodgroup> 1590: </scrap> 1591: </termdef> 1592: An example of an end-tag:<eg></termdef></eg> 1593: <termdef id="dt-content" term="Content">The 1594: <termref def="dt-text">text</termref> between the start-tag and 1595: end-tag is called the element's 1596: <term>content</term>: 1597: <scrap lang="ebnf"> 1598: <head>Content of Elements</head> 1599: <prodgroup pcw2="6" pcw4="15" pcw5="11.5"> 1600: <prod id="NT-content"><lhs>content</lhs> 1601: <rhs>(<nt def="NT-element">element</nt> | <nt def="NT-CharData">CharData</nt> 1602: | <nt def="NT-Reference">Reference</nt> | <nt def="NT-CDSect">CDSect</nt> 1603: | <nt def="NT-PI">PI</nt> | <nt def="NT-Comment">Comment</nt>)*</rhs> 1604: </prod> 1605: </prodgroup> 1606: </scrap> 1607: </termdef> 1608: <termdef id="dt-empty" term="Empty">If an element is <term>empty</term>, 1609: it must be represented either by a start-tag immediately followed 1610: by an end-tag or by an empty-element tag.</termdef> 1611: <termdef id="dt-eetag" term="empty-element tag">An 1612: <term>empty-element tag</term> takes a special form: 1613: <scrap lang="ebnf"> 1614: <head>Tags for Empty Elements</head> 1615: <prodgroup pcw2="6" pcw4="15" pcw5="11.5"> 1616: <prod id="NT-EmptyElemTag"><lhs>EmptyElemTag</lhs> 1617: <rhs>'<' <nt def="NT-Name">Name</nt> (<nt def="NT-S">S</nt> 1618: <nt def="NT-Attribute">Attribute</nt>)* <nt def="NT-S">S</nt>? 1619: '/>'</rhs> 1620: <wfc def="uniqattspec"/> 1621: </prod> 1622: </prodgroup> 1623: </scrap> 1624: </termdef> 1625: Empty-element tags may be used for any element which has no 1626: content, whether or not it is declared using the keyword 1627: <kw>EMPTY</kw>. 1628: <termref def="dt-interop">For interoperability</termref>, the empty-element 1629: tag must be used, and can only be used, for elements which are 1630: <termref def="dt-eldecl">declared</termref> <kw>EMPTY</kw>. 1631: Examples of empty elements: 1632: <eg><IMG align="left" 1633: src="http://www.w3.org/Icons/WWW/w3c_home" /> 1634: 1635: </eg> 1636: </div2> 1637: 1638: <div2 id="elemdecls"> 1639: <head>Element Type Declarations</head> 1640: 1641: The <termref def="dt-element">element</termref> structure of an 1642: <termref def="dt-xml-doc">XML document</termref> may, for 1643: <termref def="dt-valid">validation</termref> purposes, 1644: be constrained 1645: using element type and attribute-list declarations. 1646: An element type declaration constrains the element's 1647: <termref def="dt-content">content</termref>. 1648: 1649: 1650: Element type declarations often constrain which element types can 1651: appear as <termref def="dt-parentchild">children</termref> of the element. 1652: At user option, an XML processor may issue a warning 1653: when a declaration mentions an element type for which no declaration 1654: is provided, but this is not an error. 1655: <termdef id="dt-eldecl" term="Element Type declaration">An <term>element 1656: type declaration</term> takes the form: 1657: <scrap lang="ebnf"> 1658: <head>Element Type Declaration</head> 1659: <prodgroup pcw2="5.5" pcw4="18" pcw5="9"> 1660: <prod id="NT-elementdecl"><lhs>elementdecl</lhs> 1661: <rhs>'<!ELEMENT' <nt def="NT-S">S</nt> 1662: <nt def="NT-Name">Name</nt> 1663: <nt def="NT-S">S</nt> 1664: <nt def="NT-contentspec">contentspec</nt> 1665: <nt def="NT-S">S</nt>? '>'</rhs> 1666: <vc def="EDUnique"/></prod> 1667: <prod id="NT-contentspec"><lhs>contentspec</lhs> 1668: <rhs>'EMPTY' 1669: | 'ANY' 1670: | <nt def="NT-Mixed">Mixed</nt> 1671: | <nt def="NT-children">children</nt> 1672: </rhs> 1673: </prod> 1674: </prodgroup> 1675: </scrap> 1676: where the <nt def="NT-Name">Name</nt> gives the element type 1677: being declared.</termdef> 1678: 1679: 1680: <vcnote id="EDUnique"> 1681: <head>Unique Element Type Declaration</head> 1682: 1683: No element type may be declared more than once. 1684: 1685: </vcnote> 1686: 1687: Examples of element type declarations: 1688: <eg><!ELEMENT br EMPTY> 1689: <!ELEMENT p (#PCDATA|emph)* > 1690: <!ELEMENT %name.para; %content.para; > 1691: <!ELEMENT container ANY></eg> 1692: 1693: <div3 id="sec-element-content"> 1694: <head>Element Content</head> 1695: 1696: <termdef id="dt-elemcontent" term="Element content">An element <termref def="dt-stag">type</termref> has 1697: <term>element content</term> when elements of that 1698: type must contain only <termref def="dt-parentchild">child</termref> 1699: elements (no character data), optionally separated by 1700: white space (characters matching the nonterminal 1701: <nt def="NT-S">S</nt>). 1702: </termdef> 1703: In this case, the 1704: constraint includes a content model, a simple grammar governing 1705: the allowed types of the child 1706: elements and the order in which they are allowed to appear. 1707: The grammar is built on 1708: content particles (<nt def="NT-cp">cp</nt>s), which consist of names, 1709: choice lists of content particles, or 1710: sequence lists of content particles: 1711: <scrap lang="ebnf"> 1712: <head>Element-content Models</head> 1713: <prodgroup pcw2="5.5" pcw4="16" pcw5="11"> 1714: <prod id="NT-children"><lhs>children</lhs> 1715: <rhs>(<nt def="NT-choice">choice</nt> 1716: | <nt def="NT-seq">seq</nt>) 1717: ('?' | '*' | '+')?</rhs></prod> 1718: <prod id="NT-cp"><lhs>cp</lhs> 1719: <rhs>(<nt def="NT-Name">Name</nt> 1720: | <nt def="NT-choice">choice</nt> 1721: | <nt def="NT-seq">seq</nt>) 1722: ('?' | '*' | '+')?</rhs></prod> 1723: <prod id="NT-choice"><lhs>choice</lhs> 1724: <rhs>'(' <nt def="NT-S">S</nt>? cp 1725: ( <nt def="NT-S">S</nt>? '|' <nt def="NT-S">S</nt>? <nt def="NT-cp">cp</nt> )* 1726: <nt def="NT-S">S</nt>? ')'</rhs> 1727: <vc def="vc-PEinGroup"/></prod> 1728: <prod id="NT-seq"><lhs>seq</lhs> 1729: <rhs>'(' <nt def="NT-S">S</nt>? cp 1730: ( <nt def="NT-S">S</nt>? ',' <nt def="NT-S">S</nt>? <nt def="NT-cp">cp</nt> )* 1731: <nt def="NT-S">S</nt>? ')'</rhs> 1732: <vc def="vc-PEinGroup"/></prod> 1733: 1734: </prodgroup> 1735: </scrap> 1736: where each <nt def="NT-Name">Name</nt> is the type of an element which may 1737: appear as a <termref def="dt-parentchild">child</termref>. 1738: Any content 1739: particle in a choice list may appear in the <termref def="dt-elemcontent">element content</termref> at the location where 1740: the choice list appears in the grammar; 1741: content particles occurring in a sequence list must each 1742: appear in the <termref def="dt-elemcontent">element content</termref> in the 1743: order given in the list. 1744: The optional character following a name or list governs 1745: whether the element or the content particles in the list may occur one 1746: or more (<code>+</code>), zero or more (<code>*</code>), or zero or 1747: one times (<code>?</code>). 1748: The absence of such an operator means that the element or content particle 1749: must appear exactly once. 1750: This syntax 1751: and meaning are identical to those used in the productions in this 1752: specification. 1753: 1754: The content of an element matches a content model if and only if it is 1755: possible to trace out a path through the content model, obeying the 1756: sequence, choice, and repetition operators and matching each element in 1757: the content against an element type in the content model. <termref def="dt-compat">For compatibility</termref>, it is an error 1758: if an element in the document can 1759: match more than one occurrence of an element type in the content model. 1760: For more information, see <specref ref="determinism"/>. 1761:  1762:  1763: 1764: <vcnote id="vc-PEinGroup"> 1765: <head>Proper Group/PE Nesting</head> 1766: Parameter-entity 1767: <termref def="dt-repltext">replacement text</termref> must be properly nested 1768: with parenthetized groups. 1769: That is to say, if either of the opening or closing parentheses 1770: in a <nt def="NT-choice">choice</nt>, <nt def="NT-seq">seq</nt>, or 1771: <nt def="NT-Mixed">Mixed</nt> construct 1772: is contained in the replacement text for a 1773: <termref def="dt-PERef">parameter entity</termref>, 1774: both must be contained in the same replacement text. 1775: <termref def="dt-interop">For interoperability</termref>, 1776: if a parameter-entity reference appears in a 1777: <nt def="NT-choice">choice</nt>, <nt def="NT-seq">seq</nt>, or 1778: <nt def="NT-Mixed">Mixed</nt> construct, its replacement text 1779: should not be empty, and 1780: neither the first nor last non-blank 1781: character of the replacement text should be a connector 1782: (<code>|</code> or <code>,</code>). 1783: 1784: </vcnote> 1785: Examples of element-content models: 1786: <eg><!ELEMENT spec (front, body, back?)> 1787: <!ELEMENT div1 (head, (p | list | note)*, div2*)> 1788: <!ELEMENT dictionary-body (%div.mix; | %dict.mix;)*></eg> 1789: </div3> 1790: 1791: <div3 id="sec-mixed-content"> 1792: <head>Mixed Content</head> 1793: 1794: <termdef id="dt-mixed" term="Mixed Content">An element 1795: <termref def="dt-stag">type</termref> has 1796: <term>mixed content</term> when elements of that type may contain 1797: character data, optionally interspersed with 1798: <termref def="dt-parentchild">child</termref> elements.</termdef> 1799: In this case, the types of the child elements 1800: may be constrained, but not their order or their number of occurrences: 1801: <scrap lang="ebnf"> 1802: <head>Mixed-content Declaration</head> 1803: <prodgroup pcw2="5.5" pcw4="16" pcw5="11"> 1804: <prod id="NT-Mixed"><lhs>Mixed</lhs> 1805: <rhs>'(' <nt def="NT-S">S</nt>? 1806: '#PCDATA' 1807: (<nt def="NT-S">S</nt>? 1808: '|' 1809: <nt def="NT-S">S</nt>? 1810: <nt def="NT-Name">Name</nt>)* 1811: <nt def="NT-S">S</nt>? 1812: ')*' </rhs> 1813: <rhs>| '(' <nt def="NT-S">S</nt>? '#PCDATA' <nt def="NT-S">S</nt>? ')' 1814: </rhs><vc def="vc-PEinGroup"/> 1815: <vc def="vc-MixedChildrenUnique"/> 1816: </prod> 1817: 1818: </prodgroup> 1819: </scrap> 1820: where the <nt def="NT-Name">Name</nt>s give the types of elements 1821: that may appear as children. 1822: 1823: <vcnote id="vc-MixedChildrenUnique"> 1824: <head>No Duplicate Types</head> 1825: The same name must not appear more than once in a single mixed-content 1826: declaration. 1827: </vcnote> 1828: Examples of mixed content declarations: 1829: <eg><!ELEMENT p (#PCDATA|a|ul|b|i|em)*> 1830: <!ELEMENT p (#PCDATA | %font; | %phrase; | %special; | %form;)* > 1831: <!ELEMENT b (#PCDATA)></eg> 1832: </div3> 1833: </div2> 1834: 1835: <div2 id="attdecls"> 1836: <head>Attribute-List Declarations</head> 1837: 1838: <termref def="dt-attr">Attributes</termref> are used to associate 1839: name-value pairs with <termref def="dt-element">elements</termref>. 1840: Attribute specifications may appear only within <termref def="dt-stag">start-tags</termref> 1841: and <termref def="dt-eetag">empty-element tags</termref>; 1842: thus, the productions used to 1843: recognize them appear in <specref ref="sec-starttags"/>. 1844: Attribute-list 1845: declarations may be used: 1846: <ulist> 1847: <item>To define the set of attributes pertaining to a given 1848: element type.</item> 1849: <item>To establish type constraints for these 1850: attributes.</item> 1851: <item>To provide <termref def="dt-default">default values</termref> 1852: for attributes.</item> 1853: </ulist> 1854: 1855: <termdef id="dt-attdecl" term="Attribute-List Declaration"> 1856: <term>Attribute-list declarations</term> specify the name, data type, and default 1857: value (if any) of each attribute associated with a given element type: 1858: <scrap lang="ebnf"> 1859: <head>Attribute-list Declaration</head> 1860: <prod id="NT-AttlistDecl"><lhs>AttlistDecl</lhs> 1861: <rhs>'<!ATTLIST' <nt def="NT-S">S</nt> 1862: <nt def="NT-Name">Name</nt> 1863: <nt def="NT-AttDef">AttDef</nt>* 1864: <nt def="NT-S">S</nt>? '>'</rhs> 1865: </prod> 1866: <prod id="NT-AttDef"><lhs>AttDef</lhs> 1867: <rhs><nt def="NT-S">S</nt> <nt def="NT-Name">Name</nt> 1868: <nt def="NT-S">S</nt> <nt def="NT-AttType">AttType</nt> 1869: <nt def="NT-S">S</nt> <nt def="NT-DefaultDecl">DefaultDecl</nt></rhs> 1870: </prod> 1871: </scrap> 1872: The <nt def="NT-Name">Name</nt> in the 1873: <nt def="NT-AttlistDecl">AttlistDecl</nt> rule is the type of an element. At 1874: user option, an XML processor may issue a warning if attributes are 1875: declared for an element type not itself declared, but this is not an 1876: error. The <nt def="NT-Name">Name</nt> in the 1877: <nt def="NT-AttDef">AttDef</nt> rule is 1878: the name of the attribute.</termdef> 1879: 1880: When more than one <nt def="NT-AttlistDecl">AttlistDecl</nt> is provided for a 1881: given element type, the contents of all those provided are merged. When 1882: more than one definition is provided for the same attribute of a 1883: given element type, the first declaration is binding and later 1884: declarations are ignored. 1885: <termref def="dt-interop">For interoperability,</termref> writers of DTDs 1886: may choose to provide at most one attribute-list declaration 1887: for a given element type, at most one attribute definition 1888: for a given attribute name, and at least one attribute definition 1889: in each attribute-list declaration. 1890: For interoperability, an XML processor may at user option 1891: issue a warning when more than one attribute-list declaration is 1892: provided for a given element type, or more than one attribute definition 1893: is provided 1894: for a given attribute, but this is not an error. 1895: 1896: 1897: <div3 id="sec-attribute-types"> 1898: <head>Attribute Types</head> 1899: 1900: XML attribute types are of three kinds: a string type, a 1901: set of tokenized types, and enumerated types. The string type may take 1902: any literal string as a value; the tokenized types have varying lexical 1903: and semantic constraints, as noted: 1904: <scrap lang="ebnf"> 1905: <head>Attribute Types</head> 1906: <prodgroup pcw4="14" pcw5="11.5"> 1907: <prod id="NT-AttType"><lhs>AttType</lhs> 1908: <rhs><nt def="NT-StringType">StringType</nt> 1909: | <nt def="NT-TokenizedType">TokenizedType</nt> 1910: | <nt def="NT-EnumeratedType">EnumeratedType</nt> 1911: </rhs> 1912: </prod> 1913: <prod id="NT-StringType"><lhs>StringType</lhs> 1914: <rhs>'CDATA'</rhs> 1915: </prod> 1916: <prod id="NT-TokenizedType"><lhs>TokenizedType</lhs> 1917: <rhs>'ID'</rhs> 1918: <vc def="id"/> 1919: <vc def="one-id-per-el"/> 1920: <vc def="id-default"/> 1921: <rhs>| 'IDREF'</rhs> 1922: <vc def="idref"/> 1923: <rhs>| 'IDREFS'</rhs> 1924: <vc def="idref"/> 1925: <rhs>| 'ENTITY'</rhs> 1926: <vc def="entname"/> 1927: <rhs>| 'ENTITIES'</rhs> 1928: <vc def="entname"/> 1929: <rhs>| 'NMTOKEN'</rhs> 1930: <vc def="nmtok"/> 1931: <rhs>| 'NMTOKENS'</rhs> 1932: <vc def="nmtok"/></prod> 1933: </prodgroup> 1934: </scrap> 1935: 1936: <vcnote id="id"> 1937: <head>ID</head> 1938: 1939: Values of type <kw>ID</kw> must match the 1940: <nt def="NT-Name">Name</nt> production. 1941: A name must not appear more than once in 1942: an XML document as a value of this type; i.e., ID values must uniquely 1943: identify the elements which bear them. 1944: 1945: </vcnote> 1946: <vcnote id="one-id-per-el"> 1947: <head>One ID per Element Type</head> 1948: No element type may have more than one ID attribute specified. 1949: </vcnote> 1950: <vcnote id="id-default"> 1951: <head>ID Attribute Default</head> 1952: An ID attribute must have a declared default of <kw>#IMPLIED</kw> or 1953: <kw>#REQUIRED</kw>. 1954: </vcnote> 1955: <vcnote id="idref"> 1956: <head>IDREF</head> 1957: 1958: Values of type <kw>IDREF</kw> must match 1959: the <nt def="NT-Name">Name</nt> production, and 1960: values of type <kw>IDREFS</kw> must match 1961: <nt def="NT-Names">Names</nt>; 1962: each <nt def="NT-Name">Name</nt> must match the value of an ID attribute on 1963: some element in the XML document; i.e. <kw>IDREF</kw> values must 1964: match the value of some ID attribute. 1965: 1966: </vcnote> 1967: <vcnote id="entname"> 1968: <head>Entity Name</head> 1969: 1970: Values of type <kw>ENTITY</kw> 1971: must match the <nt def="NT-Name">Name</nt> production, 1972: values of type <kw>ENTITIES</kw> must match 1973: <nt def="NT-Names">Names</nt>; 1974: each <nt def="NT-Name">Name</nt> must 1975: match the 1976: name of an <termref def="dt-unparsed">unparsed entity</termref> declared in the 1977: <termref def="dt-doctype">DTD</termref>. 1978: 1979: </vcnote> 1980: <vcnote id="nmtok"> 1981: <head>Name Token</head> 1982: 1983: Values of type <kw>NMTOKEN</kw> must match the 1984: <nt def="NT-Nmtoken">Nmtoken</nt> production; 1985: values of type <kw>NMTOKENS</kw> must 1986: match <termref def="NT-Nmtokens">Nmtokens</termref>. 1987: 1988: </vcnote> 1989:  1993: <termdef id="dt-enumerated" term="Enumerated Attribute Values"><term>Enumerated attributes</term> can take one 1994: of a list of values provided in the declaration</termdef>. There are two 1995: kinds of enumerated types: 1996: <scrap lang="ebnf"> 1997: <head>Enumerated Attribute Types</head> 1998: <prod id="NT-EnumeratedType"><lhs>EnumeratedType</lhs> 1999: <rhs><nt def="NT-NotationType">NotationType</nt> 2000: | <nt def="NT-Enumeration">Enumeration</nt> 2001: </rhs></prod> 2002: <prod id="NT-NotationType"><lhs>NotationType</lhs> 2003: <rhs>'NOTATION' 2004: <nt def="NT-S">S</nt> 2005: '(' 2006: <nt def="NT-S">S</nt>? 2007: <nt def="NT-Name">Name</nt> 2008: (<nt def="NT-S">S</nt>? '|' <nt def="NT-S">S</nt>? 2009: <nt def="NT-Name">Name</nt>)* 2010: <nt def="NT-S">S</nt>? ')' 2011: </rhs> 2012: <vc def="notatn"/></prod> 2013: <prod id="NT-Enumeration"><lhs>Enumeration</lhs> 2014: <rhs>'(' <nt def="NT-S">S</nt>? 2015: <nt def="NT-Nmtoken">Nmtoken</nt> 2016: (<nt def="NT-S">S</nt>? '|' 2017: <nt def="NT-S">S</nt>? 2018: <nt def="NT-Nmtoken">Nmtoken</nt>)* 2019: <nt def="NT-S">S</nt>? 2020: ')'</rhs> 2021: <vc def="enum"/></prod> 2022: </scrap> 2023: A <kw>NOTATION</kw> attribute identifies a 2024: <termref def="dt-notation">notation</termref>, declared in the 2025: DTD with associated system and/or public identifiers, to 2026: be used in interpreting the element to which the attribute 2027: is attached. 2028: 2029: 2030: <vcnote id="notatn"> 2031: <head>Notation Attributes</head> 2032: 2033: Values of this type must match 2034: one of the <titleref href="Notations">notation</titleref> names included in 2035: the declaration; all notation names in the declaration must 2036: be declared. 2037: 2038: </vcnote> 2039: <vcnote id="enum"> 2040: <head>Enumeration</head> 2041: 2042: Values of this type 2043: must match one of the <nt def="NT-Nmtoken">Nmtoken</nt> tokens in the 2044: declaration. 2045: 2046: </vcnote> 2047: <termref def="dt-interop">For interoperability,</termref> the same 2048: <nt def="NT-Nmtoken">Nmtoken</nt> should not occur more than once in the 2049: enumerated attribute types of a single element type. 2050: 2051: </div3> 2052: 2053: <div3 id="sec-attr-defaults"> 2054: <head>Attribute Defaults</head> 2055: 2056: An <termref def="dt-attdecl">attribute declaration</termref> provides 2057: information on whether 2058: the attribute's presence is required, and if not, how an XML processor should 2059: react if a declared attribute is absent in a document. 2060: <scrap lang="ebnf"> 2061: <head>Attribute Defaults</head> 2062: <prodgroup pcw4="14" pcw5="11.5"> 2063: <prod id="NT-DefaultDecl"><lhs>DefaultDecl</lhs> 2064: <rhs>'#REQUIRED' 2065: | '#IMPLIED' </rhs> 2066: <rhs>| (('#FIXED' S)? <nt def="NT-AttValue">AttValue</nt>)</rhs> 2067: <vc def="RequiredAttr"/> 2068: <vc def="defattrvalid"/> 2069: <wfc def="CleanAttrVals"/> 2070: <vc def="FixedAttr"/> 2071: </prod> 2072: </prodgroup> 2073: </scrap> 2074: 2075: 2076: In an attribute declaration, <kw>#REQUIRED</kw> means that the 2077: attribute must always be provided, <kw>#IMPLIED</kw> that no default 2078: value is provided. 2079:  2085: <termdef id="dt-default" term="Attribute Default">If the 2086: declaration 2087: is neither <kw>#REQUIRED</kw> nor <kw>#IMPLIED</kw>, then the 2088: <nt def="NT-AttValue">AttValue</nt> value contains the declared 2089: <term>default</term> value; the <kw>#FIXED</kw> keyword states that 2090: the attribute must always have the default value. 2091: If a default value 2092: is declared, when an XML processor encounters an omitted attribute, it 2093: is to behave as though the attribute were present with 2094: the declared default value.</termdef> 2095: <vcnote id="RequiredAttr"> 2096: <head>Required Attribute</head> 2097: If the default declaration is the keyword <kw>#REQUIRED</kw>, then 2098: the attribute must be specified for 2099: all elements of the type in the attribute-list declaration. 2100: </vcnote> 2101: <vcnote id="defattrvalid"> 2102: <head>Attribute Default Legal</head> 2103: 2104: The declared 2105: default value must meet the lexical constraints of the declared attribute type. 2106: 2107: </vcnote> 2108: <vcnote id="FixedAttr"> 2109: <head>Fixed Attribute Default</head> 2110: If an attribute has a default value declared with the 2111: <kw>#FIXED</kw> keyword, instances of that attribute must 2112: match the default value. 2113: </vcnote> 2114: 2115: Examples of attribute-list declarations: 2116: <eg><!ATTLIST termdef 2117: id ID #REQUIRED 2118: name CDATA #IMPLIED> 2119: <!ATTLIST list 2120: type (bullets|ordered|glossary) "ordered"> 2121: <!ATTLIST form 2122: method CDATA #FIXED "POST"></eg> 2123: </div3> 2124: <div3 id="AVNormalize"> 2125: <head>Attribute-Value Normalization</head> 2126: Before the value of an attribute is passed to the application 2127: or checked for validity, the 2128: XML processor must normalize it as follows: 2129: <ulist> 2130: <item>a character reference is processed by appending the referenced 2131: character to the attribute value</item> 2132: <item>an entity reference is processed by recursively processing the 2133: replacement text of the entity</item> 2134: <item>a whitespace character (#x20, #xD, #xA, #x9) is processed by 2135: appending #x20 to the normalized value, except that only a single #x20 2136: is appended for a "#xD#xA" sequence that is part of an external 2137: parsed entity or the literal entity value of an internal parsed 2138: entity</item> 2139: <item>other characters are processed by appending them to the normalized 2140: value 2141: </item></ulist> 2142: 2143: If the declared value is not CDATA, then the XML processor must 2144: further process the normalized attribute value by discarding any 2145: leading and trailing space (#x20) characters, and by replacing 2146: sequences of space (#x20) characters by a single space (#x20) 2147: character. 2148: 2149: All attributes for which no declaration has been read should be treated 2150: by a non-validating parser as if declared 2151: <kw>CDATA</kw>. 2152: 2153: </div3> 2154: </div2> 2155: <div2 id="sec-condition-sect"> 2156: <head>Conditional Sections</head> 2157: <termdef id="dt-cond-section" term="conditional section"> 2158: <term>Conditional sections</term> are portions of the 2159: <termref def="dt-doctype">document type declaration external subset</termref> 2160: which are 2161: included in, or excluded from, the logical structure of the DTD based on 2162: the keyword which governs them.</termdef> 2163: <scrap lang="ebnf"> 2164: <head>Conditional Section</head> 2165: <prodgroup pcw2="9" pcw4="14.5"> 2166: <prod id="NT-conditionalSect"><lhs>conditionalSect</lhs> 2167: <rhs><nt def="NT-includeSect">includeSect</nt> 2168: | <nt def="NT-ignoreSect">ignoreSect</nt> 2169: </rhs> 2170: </prod> 2171: <prod id="NT-includeSect"><lhs>includeSect</lhs> 2172: <rhs>'<![' S? 'INCLUDE' S? '[' 2173: 2174: <nt def="NT-extSubsetDecl">extSubsetDecl</nt> 2175: ']]>' 2176: </rhs> 2177: </prod> 2178: <prod id="NT-ignoreSect"><lhs>ignoreSect</lhs> 2179: <rhs>'<![' S? 'IGNORE' S? '[' 2180: <nt def="NT-ignoreSectContents">ignoreSectContents</nt>* 2181: ']]>'</rhs> 2182: </prod> 2183: 2184: <prod id="NT-ignoreSectContents"><lhs>ignoreSectContents</lhs> 2185: <rhs><nt def="NT-Ignore">Ignore</nt> 2186: ('<![' <nt def="NT-ignoreSectContents">ignoreSectContents</nt> ']]>' 2187: <nt def="NT-Ignore">Ignore</nt>)*</rhs></prod> 2188: <prod id="NT-Ignore"><lhs>Ignore</lhs> 2189: <rhs><nt def="NT-Char">Char</nt>* - 2190: (<nt def="NT-Char">Char</nt>* ('<![' | ']]>') 2191: <nt def="NT-Char">Char</nt>*) 2192: </rhs></prod> 2193: 2194: </prodgroup> 2195: </scrap> 2196: 2197: Like the internal and external DTD subsets, a conditional section 2198: may contain one or more complete declarations, 2199: comments, processing instructions, 2200: or nested conditional sections, intermingled with white space. 2201: 2202: If the keyword of the 2203: conditional section is <kw>INCLUDE</kw>, then the contents of the conditional 2204: section are part of the DTD. 2205: If the keyword of the conditional 2206: section is <kw>IGNORE</kw>, then the contents of the conditional section are 2207: not logically part of the DTD. 2208: Note that for reliable parsing, the contents of even ignored 2209: conditional sections must be read in order to 2210: detect nested conditional sections and ensure that the end of the 2211: outermost (ignored) conditional section is properly detected. 2212: If a conditional section with a 2213: keyword of <kw>INCLUDE</kw> occurs within a larger conditional 2214: section with a keyword of <kw>IGNORE</kw>, both the outer and the 2215: inner conditional sections are ignored. 2216: If the keyword of the conditional section is a 2217: parameter-entity reference, the parameter entity must be replaced by its 2218: content before the processor decides whether to 2219: include or ignore the conditional section. 2220: An example: 2221: <eg><!ENTITY % draft 'INCLUDE' > 2222: <!ENTITY % final 'IGNORE' > 2223: 2224: <![%draft;[ 2225: <!ELEMENT book (comments*, title, body, supplements?)> 2226: ]]> 2227: <![%final;[ 2228: <!ELEMENT book (title, body, supplements?)> 2229: ]]> 2230: </eg> 2231: 2232: </div2> 2233: 2234: 2235:  2256: 2257: </div1> 2258:  2259: 2260: <div1 id="sec-physical-struct"> 2261: <head>Physical Structures</head> 2262: 2263: <termdef id="dt-entity" term="Entity">An XML document may consist 2264: of one or many storage units. These are called 2265: <term>entities</term>; they all have <term>content</term> and are all 2266: (except for the document entity, see below, and 2267: the <termref def="dt-doctype">external DTD subset</termref>) 2268: identified by <term>name</term>. 2269: </termdef> 2270: Each XML document has one entity 2271: called the <termref def="dt-docent">document entity</termref>, which serves 2272: as the starting point for the <termref def="dt-xml-proc">XML 2273: processor</termref> and may contain the whole document. 2274: Entities may be either parsed or unparsed. 2275: <termdef id="dt-parsedent" term="Text Entity">A <term>parsed entity's</term> 2276: contents are referred to as its 2277: <termref def="dt-repltext">replacement text</termref>; 2278: this <termref def="dt-text">text</termref> is considered an 2279: integral part of the document.</termdef> 2280: 2281: <termdef id="dt-unparsed" term="Unparsed Entity">An 2282: <term>unparsed entity</term> 2283: is a resource whose contents may or may not be 2284: <termref def="dt-text">text</termref>, and if text, may not be XML. 2285: Each unparsed entity 2286: has an associated <termref def="dt-notation">notation</termref>, identified by name. 2287: Beyond a requirement 2288: that an XML processor make the identifiers for the entity and 2289: notation available to the application, 2290: XML places no constraints on the contents of unparsed entities.</termdef> 2291: 2292: 2293: Parsed entities are invoked by name using entity references; 2294: unparsed entities by name, given in the value of <kw>ENTITY</kw> 2295: or <kw>ENTITIES</kw> 2296: attributes. 2297: <termdef id="gen-entity" term="general entity"><term>General entities</term> 2298: are entities for use within the document content. 2299: In this specification, general entities are sometimes referred 2300: to with the unqualified term <emph>entity</emph> when this leads 2301: to no ambiguity.</termdef> 2302: <termdef id="dt-PE" term="Parameter entity">Parameter entities 2303: are parsed entities for use within the DTD.</termdef> 2304: These two types of entities use different forms of reference and 2305: are recognized in different contexts. 2306: Furthermore, they occupy different namespaces; a parameter entity and 2307: a general entity with the same name are two distinct entities. 2308: 2309: 2310: <div2 id="sec-references"> 2311: <head>Character and Entity References</head> 2312: <termdef id="dt-charref" term="Character Reference"> 2313: A <term>character reference</term> refers to a specific character in the 2314: ISO/IEC 10646 character set, for example one not directly accessible from 2315: available input devices. 2316: <scrap lang="ebnf"> 2317: <head>Character Reference</head> 2318: <prod id="NT-CharRef"><lhs>CharRef</lhs> 2319: <rhs>'&#' [0-9]+ ';' </rhs> 2320: <rhs>| '&hcro;' [0-9a-fA-F]+ ';'</rhs> 2321: <wfc def="wf-Legalchar"/> 2322: </prod> 2323: </scrap> 2324: <wfcnote id="wf-Legalchar"> 2325: <head>Legal Character</head> 2326: Characters referred to using character references must 2327: match the production for 2328: <termref def="NT-Char">Char</termref>. 2329: </wfcnote> 2330: If the character reference begins with "<code>&#x</code>", the digits and 2331: letters up to the terminating <code>;</code> provide a hexadecimal 2332: representation of the character's code point in ISO/IEC 10646. 2333: If it begins just with "<code>&#</code>", the digits up to the terminating 2334: <code>;</code> provide a decimal representation of the character's 2335: code point. 2336: </termdef> 2337: 2338: <termdef id="dt-entref" term="Entity Reference">An <term>entity 2339: reference</term> refers to the content of a named entity.</termdef> 2340: <termdef id="dt-GERef" term="General Entity Reference">References to 2341: parsed general entities 2342: use ampersand (<code>&</code>) and semicolon (<code>;</code>) as 2343: delimiters.</termdef> 2344: <termdef id="dt-PERef" term="Parameter-entity reference"> 2345: <term>Parameter-entity references</term> use percent-sign (<code>%</code>) and 2346: semicolon 2347: (<code>;</code>) as delimiters.</termdef> 2348: 2349: <scrap lang="ebnf"> 2350: <head>Entity Reference</head> 2351: <prod id="NT-Reference"><lhs>Reference</lhs> 2352: <rhs><nt def="NT-EntityRef">EntityRef</nt> 2353: | <nt def="NT-CharRef">CharRef</nt></rhs></prod> 2354: <prod id="NT-EntityRef"><lhs>EntityRef</lhs> 2355: <rhs>'&' <nt def="NT-Name">Name</nt> ';'</rhs> 2356: <wfc def="wf-entdeclared"/> 2357: <vc def="vc-entdeclared"/> 2358: <wfc def="textent"/> 2359: <wfc def="norecursion"/> 2360: </prod> 2361: <prod id="NT-PEReference"><lhs>PEReference</lhs> 2362: <rhs>'%' <nt def="NT-Name">Name</nt> ';'</rhs> 2363: <vc def="vc-entdeclared"/> 2364: <wfc def="norecursion"/> 2365: <wfc def="indtd"/> 2366: </prod> 2367: </scrap> 2368: 2369: <wfcnote id="wf-entdeclared"> 2370: <head>Entity Declared</head> 2371: In a document without any DTD, a document with only an internal 2372: DTD subset which contains no parameter entity references, or a document with 2373: "<code>standalone='yes'</code>", 2374: the <nt def="NT-Name">Name</nt> given in the entity reference must 2375: <termref def="dt-match">match</termref> that in an 2376: <titleref href="sec-entity-decl">entity declaration</titleref>, except that 2377: well-formed documents need not declare 2378: any of the following entities: &magicents;. 2379: The declaration of a parameter entity must precede any reference to it. 2380: Similarly, the declaration of a general entity must precede any 2381: reference to it which appears in a default value in an attribute-list 2382: declaration. 2383: Note that if entities are declared in the external subset or in 2384: external parameter entities, a non-validating processor is 2385: <titleref href="include-if-valid">not obligated to</titleref> read 2386: and process their declarations; for such documents, the rule that 2387: an entity must be declared is a well-formedness constraint only 2388: if <titleref href="sec-rmd">standalone='yes'</titleref>. 2389: </wfcnote> 2390: <vcnote id="vc-entdeclared"> 2391: <head>Entity Declared</head> 2392: In a document with an external subset or external parameter 2393: entities with "<code>standalone='no'</code>", 2394: the <nt def="NT-Name">Name</nt> given in the entity reference must <termref def="dt-match">match</termref> that in an 2395: <titleref href="sec-entity-decl">entity declaration</titleref>. 2396: For interoperability, valid documents should declare the entities 2397: &magicents;, in the form 2398: specified in <specref ref="sec-predefined-ent"/>. 2399: The declaration of a parameter entity must precede any reference to it. 2400: Similarly, the declaration of a general entity must precede any 2401: reference to it which appears in a default value in an attribute-list 2402: declaration. 2403: </vcnote> 2404:  2405: <wfcnote id="textent"> 2406: <head>Parsed Entity</head> 2407: 2408: An entity reference must not contain the name of an <termref def="dt-unparsed">unparsed entity</termref>. Unparsed entities may be referred 2409: to only in <termref def="dt-attrval">attribute values</termref> declared to 2410: be of type <kw>ENTITY</kw> or <kw>ENTITIES</kw>. 2411: 2412: </wfcnote> 2413: <wfcnote id="norecursion"> 2414: <head>No Recursion</head> 2415: 2416: A parsed entity must not contain a recursive reference to itself, 2417: either directly or indirectly. 2418: 2419: </wfcnote> 2420: <wfcnote id="indtd"> 2421: <head>In DTD</head> 2422: 2423: Parameter-entity references may only appear in the 2424: <termref def="dt-doctype">DTD</termref>. 2425: 2426: </wfcnote> 2427: Examples of character and entity references: 2428: <eg>Type <key>less-than</key> (&hcro;3C;) to save options. 2429: This document was prepared on &docdate; and 2430: is classified &security-level;.</eg> 2431: Example of a parameter-entity reference: 2432: <eg><![CDATA[ 2433: <!ENTITY % ISOLat2 2434: SYSTEM "http://www.xml.com/iso/isolat2-xml.entities" > 2435:  2436: %ISOLat2;]]></eg> 2437: </div2> 2438: 2439: <div2 id="sec-entity-decl"> 2440: <head>Entity Declarations</head> 2441: 2442: <termdef id="dt-entdecl" term="entity declaration"> 2443: Entities are declared thus: 2444: <scrap lang="ebnf"> 2445: <head>Entity Declaration</head> 2446: <prodgroup pcw2="5" pcw4="18.5"> 2447: <prod id="NT-EntityDecl"><lhs>EntityDecl</lhs> 2448: <rhs><nt def="NT-GEDecl">GEDecl</nt> | <nt def="NT-PEDecl">PEDecl</nt></rhs> 2450:  2451: </prod> 2452: <prod id="NT-GEDecl"><lhs>GEDecl</lhs> 2453: <rhs>'<!ENTITY' <nt def="NT-S">S</nt> <nt def="NT-Name">Name</nt> 2454: <nt def="NT-S">S</nt> <nt def="NT-EntityDef">EntityDef</nt> 2455: <nt def="NT-S">S</nt>? '>'</rhs> 2456: </prod> 2457: <prod id="NT-PEDecl"><lhs>PEDecl</lhs> 2458: <rhs>'<!ENTITY' <nt def="NT-S">S</nt> '%' <nt def="NT-S">S</nt> 2459: <nt def="NT-Name">Name</nt> <nt def="NT-S">S</nt> 2460: <nt def="NT-PEDef">PEDef</nt> <nt def="NT-S">S</nt>? '>'</rhs> 2461:  2462: </prod> 2463: <prod id="NT-EntityDef"><lhs>EntityDef</lhs> 2464: <rhs><nt def="NT-EntityValue">EntityValue</nt> 2465: | (<nt def="NT-ExternalID">ExternalID</nt> 2467: <nt def="NT-NDataDecl">NDataDecl</nt>?)</rhs> 2468:  2469: </prod> 2470:  2471: <prod id="NT-PEDef"><lhs>PEDef</lhs> 2472: <rhs><nt def="NT-EntityValue">EntityValue</nt> 2473: | <nt def="NT-ExternalID">ExternalID</nt></rhs></prod> 2474: </prodgroup> 2475: </scrap> 2476: The <nt def="NT-Name">Name</nt> identifies the entity in an 2477: <termref def="dt-entref">entity reference</termref> or, in the case of an 2478: unparsed entity, in the value of an <kw>ENTITY</kw> or <kw>ENTITIES</kw> 2479: attribute. 2480: If the same entity is declared more than once, the first declaration 2481: encountered is binding; at user option, an XML processor may issue a 2482: warning if entities are declared multiple times.</termdef> 2483: 2484: 2485: <div3 id="sec-internal-ent"> 2486: <head>Internal Entities</head> 2487: 2488: <termdef id="dt-internent" term="Internal Entity Replacement Text">If 2489: the entity definition is an 2490: <nt def="NT-EntityValue">EntityValue</nt>, 2491: the defined entity is called an <term>internal entity</term>. 2492: There is no separate physical 2493: storage object, and the content of the entity is given in the 2494: declaration. </termdef> 2495: Note that some processing of entity and character references in the 2496: <termref def="dt-litentval">literal entity value</termref> may be required to 2497: produce the correct <termref def="dt-repltext">replacement 2498: text</termref>: see <specref ref="intern-replacement"/>. 2499: 2500: An internal entity is a <termref def="dt-parsedent">parsed 2501: entity</termref>. 2502: Example of an internal entity declaration: 2503: <eg><!ENTITY Pub-Status "This is a pre-release of the 2504: specification."></eg> 2505: </div3> 2506: 2507: <div3 id="sec-external-ent"> 2508: <head>External Entities</head> 2509: 2510: <termdef id="dt-extent" term="External Entity">If the entity is not 2511: internal, it is an <term>external 2512: entity</term>, declared as follows: 2513: <scrap lang="ebnf"> 2514: <head>External Entity Declaration</head> 2515:  2518: <prod id="NT-ExternalID"><lhs>ExternalID</lhs> 2519: <rhs>'SYSTEM' <nt def="NT-S">S</nt> 2520: <nt def="NT-SystemLiteral">SystemLiteral</nt></rhs> 2521: <rhs>| 'PUBLIC' <nt def="NT-S">S</nt> 2522: <nt def="NT-PubidLiteral">PubidLiteral</nt> 2523: <nt def="NT-S">S</nt> 2524: <nt def="NT-SystemLiteral">SystemLiteral</nt> 2525: </rhs> 2526: </prod> 2527: <prod id="NT-NDataDecl"><lhs>NDataDecl</lhs> 2528: <rhs><nt def="NT-S">S</nt> 'NDATA' <nt def="NT-S">S</nt> 2529: <nt def="NT-Name">Name</nt></rhs> 2530: <vc def="not-declared"/></prod> 2531: </scrap> 2532: If the <nt def="NT-NDataDecl">NDataDecl</nt> is present, this is a 2533: general <termref def="dt-unparsed">unparsed 2534: entity</termref>; otherwise it is a parsed entity.</termdef> 2535: <vcnote id="not-declared"> 2536: <head>Notation Declared</head> 2537: 2538: The <nt def="NT-Name">Name</nt> must match the declared name of a 2539: <termref def="dt-notation">notation</termref>. 2540: 2541: </vcnote> 2542: <termdef id="dt-sysid" term="System Identifier">The 2543: <nt def="NT-SystemLiteral">SystemLiteral</nt> 2544: is called the entity's <term>system identifier</term>. It is a URI, 2545: which may be used to retrieve the entity.</termdef> 2546: Note that the hash mark (<code>#</code>) and fragment identifier 2547: frequently used with URIs are not, formally, part of the URI itself; 2548: an XML processor may signal an error if a fragment identifier is 2549: given as part of a system identifier. 2550: Unless otherwise provided by information outside the scope of this 2551: specification (e.g. a special XML element type defined by a particular 2552: DTD, or a processing instruction defined by a particular application 2553: specification), relative URIs are relative to the location of the 2554: resource within which the entity declaration occurs. 2555: A URI might thus be relative to the 2556: <termref def="dt-docent">document entity</termref>, to the entity 2557: containing the <termref def="dt-doctype">external DTD subset</termref>, 2558: or to some other <termref def="dt-extent">external parameter entity</termref>. 2559: 2560: An XML processor should handle a non-ASCII character in a URI by 2561: representing the character in UTF-8 as one or more bytes, and then 2562: escaping these bytes with the URI escaping mechanism (i.e., by 2563: converting each byte to %HH, where HH is the hexadecimal notation of the 2564: byte value). 2565: <termdef id="dt-pubid" term="Public identifier"> 2566: In addition to a system identifier, an external identifier may 2567: include a <term>public identifier</term>.</termdef> 2568: An XML processor attempting to retrieve the entity's content may use the public 2569: identifier to try to generate an alternative URI. If the processor 2570: is unable to do so, it must use the URI specified in the system 2571: literal. Before a match is attempted, all strings 2572: of white space in the public identifier must be normalized to single space characters (#x20), 2573: and leading and trailing white space must be removed. 2574: Examples of external entity declarations: 2575: <eg><!ENTITY open-hatch 2576: SYSTEM "http://www.textuality.com/boilerplate/OpenHatch.xml"> 2577: <!ENTITY open-hatch 2578: PUBLIC "-//Textuality//TEXT Standard open-hatch boilerplate//EN" 2579: "http://www.textuality.com/boilerplate/OpenHatch.xml"> 2580: <!ENTITY hatch-pic 2581: SYSTEM "../grafix/OpenHatch.gif" 2582: NDATA gif ></eg> 2583: </div3> 2584: 2585: </div2> 2586: 2587: <div2 id="TextEntities"> 2588: <head>Parsed Entities</head> 2589: <div3 id="sec-TextDecl"> 2590: <head>The Text Declaration</head> 2591: External parsed entities may each begin with a <term>text 2592: declaration</term>. 2593: <scrap lang="ebnf"> 2594: <head>Text Declaration</head> 2595: <prodgroup pcw4="12.5" pcw5="13"> 2596: <prod id="NT-TextDecl"><lhs>TextDecl</lhs> 2597: <rhs>&xmlpio; 2598: <nt def="NT-VersionInfo">VersionInfo</nt>? 2599: <nt def="NT-EncodingDecl">EncodingDecl</nt> 2600: <nt def="NT-S">S</nt>? &pic;</rhs> 2601: </prod> 2602: </prodgroup> 2603: </scrap> 2604: 2605: The text declaration must be provided literally, not 2606: by reference to a parsed entity. 2607: No text declaration may appear at any position other than the beginning of 2608: an external parsed entity. 2609: </div3> 2610: <div3 id="wf-entities"> 2611: <head>Well-Formed Parsed Entities</head> 2612: The document entity is well-formed if it matches the production labeled 2613: <nt def="NT-document">document</nt>. 2614: An external general 2615: parsed entity is well-formed if it matches the production labeled 2616: <nt def="NT-extParsedEnt">extParsedEnt</nt>. 2617: An external parameter 2618: entity is well-formed if it matches the production labeled 2619: <nt def="NT-extPE">extPE</nt>. 2620: <scrap lang="ebnf"> 2621: <head>Well-Formed External Parsed Entity</head> 2622: <prod id="NT-extParsedEnt"><lhs>extParsedEnt</lhs> 2623: <rhs><nt def="NT-TextDecl">TextDecl</nt>? 2624: <nt def="NT-content">content</nt></rhs> 2625: </prod> 2626: <prod id="NT-extPE"><lhs>extPE</lhs> 2627: <rhs><nt def="NT-TextDecl">TextDecl</nt>? 2628: <nt def="NT-extSubsetDecl">extSubsetDecl</nt></rhs> 2629: </prod> 2630: </scrap> 2631: An internal general parsed entity is well-formed if its replacement text 2632: matches the production labeled 2633: <nt def="NT-content">content</nt>. 2634: All internal parameter entities are well-formed by definition. 2635: 2636: A consequence of well-formedness in entities is that the logical 2637: and physical structures in an XML document are properly nested; no 2638: <termref def="dt-stag">start-tag</termref>, 2639: <termref def="dt-etag">end-tag</termref>, 2640: <termref def="dt-empty">empty-element tag</termref>, 2641: <termref def="dt-element">element</termref>, 2642: <termref def="dt-comment">comment</termref>, 2643: <termref def="dt-pi">processing instruction</termref>, 2644: <termref def="dt-charref">character 2645: reference</termref>, or 2646: <termref def="dt-entref">entity reference</termref> 2647: can begin in one entity and end in another. 2648: </div3> 2649: <div3 id="charencoding"> 2650: <head>Character Encoding in Entities</head> 2651: 2652: Each external parsed entity in an XML document may use a different 2653: encoding for its characters. All XML processors must be able to read 2654: entities in either UTF-8 or UTF-16. 2655: 2656: 2657: Entities encoded in UTF-16 must 2658: begin with the Byte Order Mark described by ISO/IEC 10646 Annex E and 2659: Unicode Appendix B (the ZERO WIDTH NO-BREAK SPACE character, #xFEFF). 2660: This is an encoding signature, not part of either the markup or the 2661: character data of the XML document. 2662: XML processors must be able to use this character to 2663: differentiate between UTF-8 and UTF-16 encoded documents. 2664: Although an XML processor is required to read only entities in 2665: the UTF-8 and UTF-16 encodings, it is recognized that other encodings are 2666: used around the world, and it may be desired for XML processors 2667: to read entities that use them. 2668: Parsed entities which are stored in an encoding other than 2669: UTF-8 or UTF-16 must begin with a <titleref href="TextDecl">text 2670: declaration</titleref> containing an encoding declaration: 2671: <scrap lang="ebnf"> 2672: <head>Encoding Declaration</head> 2673: <prod id="NT-EncodingDecl"><lhs>EncodingDecl</lhs> 2674: <rhs><nt def="NT-S">S</nt> 2675: 'encoding' <nt def="NT-Eq">Eq</nt> 2676: ('"' <nt def="NT-EncName">EncName</nt> '"' | 2677: "'" <nt def="NT-EncName">EncName</nt> "'" ) 2678: </rhs> 2679: </prod> 2680: <prod id="NT-EncName"><lhs>EncName</lhs> 2681: <rhs>[A-Za-z] ([A-Za-z0-9._] | '-')*</rhs> 2682: <com>Encoding name contains only Latin characters</com> 2683: </prod> 2684: </scrap> 2685: In the <termref def="dt-docent">document entity</termref>, the encoding 2686: declaration is part of the <termref def="dt-xmldecl">XML declaration</termref>. 2687: The <nt def="NT-EncName">EncName</nt> is the name of the encoding used. 2688: 2689:  2690: In an encoding declaration, the values 2691: "<code>UTF-8</code>", 2692: "<code>UTF-16</code>", 2693: "<code>ISO-10646-UCS-2</code>", and 2694: "<code>ISO-10646-UCS-4</code>" should be 2695: used for the various encodings and transformations of Unicode / 2696: ISO/IEC 10646, the values 2697: "<code>ISO-8859-1</code>", 2698: "<code>ISO-8859-2</code>", ... 2699: "<code>ISO-8859-9</code>" should be used for the parts of ISO 8859, and 2700: the values 2701: "<code>ISO-2022-JP</code>", 2702: "<code>Shift_JIS</code>", and 2703: "<code>EUC-JP</code>" 2704: should be used for the various encoded forms of JIS X-0208-1997. XML 2705: processors may recognize other encodings; it is recommended that 2706: character encodings registered (as <emph>charset</emph>s) 2707: with the Internet Assigned Numbers 2708: Authority <bibref ref="IANA"/>, other than those just listed, should be 2709: referred to 2710: using their registered names. 2711: Note that these registered names are defined to be 2712: case-insensitive, so processors wishing to match against them 2713: should do so in a case-insensitive 2714: way. 2715: In the absence of information provided by an external 2716: transport protocol (e.g. HTTP or MIME), 2717: it is an <termref def="dt-error">error</termref> for an entity including 2718: an encoding declaration to be presented to the XML processor 2719: in an encoding other than that named in the declaration, 2720: for an encoding declaration to occur other than at the beginning 2721: of an external entity, or for 2722: an entity which begins with neither a Byte Order Mark nor an encoding 2723: declaration to use an encoding other than UTF-8. 2724: Note that since ASCII 2725: is a subset of UTF-8, ordinary ASCII entities do not strictly need 2726: an encoding declaration. 2727: 2728: It is a <termref def="dt-fatal">fatal error</termref> when an XML processor 2729: encounters an entity with an encoding that it is unable to process. 2730: Examples of encoding declarations: 2731: <eg><?xml encoding='UTF-8'?> 2732: <?xml encoding='EUC-JP'?></eg> 2733: </div3> 2734: </div2> 2735: <div2 id="entproc"> 2736: <head>XML Processor Treatment of Entities and References</head> 2737: The table below summarizes the contexts in which character references, 2738: entity references, and invocations of unparsed entities might appear and the 2739: required behavior of an <termref def="dt-xml-proc">XML processor</termref> in 2740: each case. 2741: The labels in the leftmost column describe the recognition context: 2742: <glist> 2743: <gitem><label>Reference in Content</label> 2744: <def>as a reference 2745: anywhere after the <termref def="dt-stag">start-tag</termref> and 2746: before the <termref def="dt-etag">end-tag</termref> of an element; corresponds 2747: to the nonterminal <nt def="NT-content">content</nt>.</def> 2748: </gitem> 2749: <gitem> 2750: <label>Reference in Attribute Value</label> 2751: <def>as a reference within either the value of an attribute in a 2752: <termref def="dt-stag">start-tag</termref>, or a default 2753: value in an <termref def="dt-attdecl">attribute declaration</termref>; 2754: corresponds to the nonterminal 2755: <nt def="NT-AttValue">AttValue</nt>.</def></gitem> 2756: <gitem> 2757: <label>Occurs as Attribute Value</label> 2758: <def>as a <nt def="NT-Name">Name</nt>, not a reference, appearing either as 2759: the value of an 2760: attribute which has been declared as type <kw>ENTITY</kw>, or as one of 2761: the space-separated tokens in the value of an attribute which has been 2762: declared as type <kw>ENTITIES</kw>. 2763: </def></gitem> 2764: <gitem><label>Reference in Entity Value</label> 2765: <def>as a reference 2766: within a parameter or internal entity's 2767: <termref def="dt-litentval">literal entity value</termref> in 2768: the entity's declaration; corresponds to the nonterminal 2769: <nt def="NT-EntityValue">EntityValue</nt>.</def></gitem> 2770: <gitem><label>Reference in DTD</label> 2771: <def>as a reference within either the internal or external subsets of the 2772: <termref def="dt-doctype">DTD</termref>, but outside 2773: of an <nt def="NT-EntityValue">EntityValue</nt> or 2774: <nt def="NT-AttValue">AttValue</nt>.</def> 2775: </gitem> 2776: </glist> 2777: <htable border="1" cellpadding="7" align="center"> 2778: <htbody> 2779: <tr><td bgcolor="&cellback;" rowspan="2" colspan="1"/> 2780: <td bgcolor="&cellback;" align="center" valign="bottom" colspan="4">Entity Type</td> 2781: <td bgcolor="&cellback;" rowspan="2" align="center">Character</td> 2782: </tr> 2783: <tr align="center" valign="bottom"> 2784: <td bgcolor="&cellback;">Parameter</td> 2785: <td bgcolor="&cellback;">Internal 2786: General</td> 2787: <td bgcolor="&cellback;">External Parsed 2788: General</td> 2789: <td bgcolor="&cellback;">Unparsed</td> 2790: </tr> 2791: <tr align="center" valign="middle"> 2792: 2793: <td bgcolor="&cellback;" align="right">Reference 2794: in Content</td> 2795: <td bgcolor="&cellback;"><titleref href="not-recognized">Not recognized</titleref></td> 2796: <td bgcolor="&cellback;"><titleref href="included">Included</titleref></td> 2797: <td bgcolor="&cellback;"><titleref href="include-if-valid">Included if validating</titleref></td> 2798: <td bgcolor="&cellback;"><titleref href="forbidden">Forbidden</titleref></td> 2799: <td bgcolor="&cellback;"><titleref href="included">Included</titleref></td> 2800: </tr> 2801: <tr align="center" valign="middle"> 2802: <td bgcolor="&cellback;" align="right">Reference 2803: in Attribute Value</td> 2804: <td bgcolor="&cellback;"><titleref href="not-recognized">Not recognized</titleref></td> 2805: <td bgcolor="&cellback;"><titleref href="inliteral">Included in literal</titleref></td> 2806: <td bgcolor="&cellback;"><titleref href="forbidden">Forbidden</titleref></td> 2807: <td bgcolor="&cellback;"><titleref href="forbidden">Forbidden</titleref></td> 2808: <td bgcolor="&cellback;"><titleref href="included">Included</titleref></td> 2809: </tr> 2810: <tr align="center" valign="middle"> 2811: <td bgcolor="&cellback;" align="right">Occurs as 2812: Attribute Value</td> 2813: <td bgcolor="&cellback;"><titleref href="not-recognized">Not recognized</titleref></td> 2814: <td bgcolor="&cellback;"><titleref href="not-recognized">Forbidden</titleref></td> 2815: <td bgcolor="&cellback;"><titleref href="not-recognized">Forbidden</titleref></td> 2816: <td bgcolor="&cellback;"><titleref href="notify">Notify</titleref></td> 2817: <td bgcolor="&cellback;"><titleref href="not recognized">Not recognized</titleref></td> 2818: </tr> 2819: <tr align="center" valign="middle"> 2820: <td bgcolor="&cellback;" align="right">Reference 2821: in EntityValue</td> 2822: <td bgcolor="&cellback;"><titleref href="inliteral">Included in literal</titleref></td> 2823: <td bgcolor="&cellback;"><titleref href="bypass">Bypassed</titleref></td> 2824: <td bgcolor="&cellback;"><titleref href="bypass">Bypassed</titleref></td> 2825: <td bgcolor="&cellback;"><titleref href="forbidden">Forbidden</titleref></td> 2826: <td bgcolor="&cellback;"><titleref href="included">Included</titleref></td> 2827: </tr> 2828: <tr align="center" valign="middle"> 2829: <td bgcolor="&cellback;" align="right">Reference 2830: in DTD</td> 2831: <td bgcolor="&cellback;"><titleref href="as-PE">Included as PE</titleref></td> 2832: <td bgcolor="&cellback;"><titleref href="forbidden">Forbidden</titleref></td> 2833: <td bgcolor="&cellback;"><titleref href="forbidden">Forbidden</titleref></td> 2834: <td bgcolor="&cellback;"><titleref href="forbidden">Forbidden</titleref></td> 2835: <td bgcolor="&cellback;"><titleref href="forbidden">Forbidden</titleref></td> 2836: </tr> 2837: </htbody> 2838: </htable> 2839: <div3 id="not-recognized"> 2840: <head>Not Recognized</head> 2841: Outside the DTD, the <code>%</code> character has no 2842: special significance; thus, what would be parameter entity references in the 2843: DTD are not recognized as markup in <nt def="NT-content">content</nt>. 2844: Similarly, the names of unparsed entities are not recognized except 2845: when they appear in the value of an appropriately declared attribute. 2846: 2847: </div3> 2848: <div3 id="included"> 2849: <head>Included</head> 2850: <termdef id="dt-include" term="Include">An entity is 2851: <term>included</term> when its 2852: <termref def="dt-repltext">replacement text</termref> is retrieved 2853: and processed, in place of the reference itself, 2854: as though it were part of the document at the location the 2855: reference was recognized. 2856: The replacement text may contain both 2857: <termref def="dt-chardata">character data</termref> 2858: and (except for parameter entities) <termref def="dt-markup">markup</termref>, 2859: which must be recognized in 2860: the usual way, except that the replacement text of entities used to escape 2861: markup delimiters (the entities &magicents;) is always treated as 2862: data. (The string "<code>AT&amp;T;</code>" expands to 2863: "<code>AT&T;</code>" and the remaining ampersand is not recognized 2864: as an entity-reference delimiter.) 2865: A character reference is <term>included</term> when the indicated 2866: character is processed in place of the reference itself. 2867: </termdef> 2868: </div3> 2869: <div3 id="include-if-valid"> 2870: <head>Included If Validating</head> 2871: When an XML processor recognizes a reference to a parsed entity, in order 2872: to <termref def="dt-valid">validate</termref> 2873: the document, the processor must 2874: <termref def="dt-include">include</termref> its 2875: replacement text. 2876: If the entity is external, and the processor is not 2877: attempting to validate the XML document, the 2878: processor <termref def="dt-may">may</termref>, but need not, 2879: include the entity's replacement text. 2880: If a non-validating parser does not include the replacement text, 2881: it must inform the application that it recognized, but did not 2882: read, the entity. 2883: This rule is based on the recognition that the automatic inclusion 2884: provided by the SGML and XML entity mechanism, primarily designed 2885: to support modularity in authoring, is not necessarily 2886: appropriate for other applications, in particular document browsing. 2887: Browsers, for example, when encountering an external parsed entity reference, 2888: might choose to provide a visual indication of the entity's 2889: presence and retrieve it for display only on demand. 2890: 2891: </div3> 2892: <div3 id="forbidden"> 2893: <head>Forbidden</head> 2894: The following are forbidden, and constitute 2895: <termref def="dt-fatal">fatal</termref> errors: 2896: <ulist> 2897: <item>the appearance of a reference to an 2898: <termref def="dt-unparsed">unparsed entity</termref>. 2899: </item> 2900: <item>the appearance of any character or general-entity reference in the 2901: DTD except within an <nt def="NT-EntityValue">EntityValue</nt> or 2902: <nt def="NT-AttValue">AttValue</nt>.</item> 2903: <item>a reference to an external entity in an attribute value. 2904: </item> 2905: </ulist> 2906: 2907: </div3> 2908: <div3 id="inliteral"> 2909: <head>Included in Literal</head> 2910: When an <termref def="dt-entref">entity reference</termref> appears in an 2911: attribute value, or a parameter entity reference appears in a literal entity 2912: value, its <termref def="dt-repltext">replacement text</termref> is 2913: processed in place of the reference itself as though it 2914: were part of the document at the location the reference was recognized, 2915: except that a single or double quote character in the replacement text 2916: is always treated as a normal data character and will not terminate the 2917: literal. 2918: For example, this is well-formed: 2919: <eg><![CDATA[<!ENTITY % YN '"Yes"' > 2920: <!ENTITY WhatHeSaid "He said &YN;" >]]></eg> 2921: while this is not: 2922: <eg><!ENTITY EndAttr "27'" > 2923: <element attribute='a-&EndAttr;></eg> 2924: </div3> 2925: <div3 id="notify"> 2926: <head>Notify</head> 2927: When the name of an <termref def="dt-unparsed">unparsed 2928: entity</termref> appears as a token in the 2929: value of an attribute of declared type <kw>ENTITY</kw> or <kw>ENTITIES</kw>, 2930: a validating processor must inform the 2931: application of the <termref def="dt-sysid">system</termref> 2932: and <termref def="dt-pubid">public</termref> (if any) 2933: identifiers for both the entity and its associated 2934: <termref def="dt-notation">notation</termref>. 2935: </div3> 2936: <div3 id="bypass"> 2937: <head>Bypassed</head> 2938: When a general entity reference appears in the 2939: <nt def="NT-EntityValue">EntityValue</nt> in an entity declaration, 2940: it is bypassed and left as is. 2941: </div3> 2942: <div3 id="as-PE"> 2943: <head>Included as PE</head> 2944: Just as with external parsed entities, parameter entities 2945: need only be <titleref href="include-if-valid">included if 2946: validating</titleref>. 2947: When a parameter-entity reference is recognized in the DTD 2948: and included, its 2949: <termref def="dt-repltext">replacement 2950: text</termref> is enlarged by the attachment of one leading and one following 2951: space (#x20) character; the intent is to constrain the replacement 2952: text of parameter 2953: entities to contain an integral number of grammatical tokens in the DTD. 2954: 2955: </div3> 2956: 2957: </div2> 2958: <div2 id="intern-replacement"> 2959: <head>Construction of Internal Entity Replacement Text</head> 2960: In discussing the treatment 2961: of internal entities, it is 2962: useful to distinguish two forms of the entity's value. 2963: <termdef id="dt-litentval" term="Literal Entity Value">The <term>literal 2964: entity value</term> is the quoted string actually 2965: present in the entity declaration, corresponding to the 2966: non-terminal <nt def="NT-EntityValue">EntityValue</nt>.</termdef> 2967: <termdef id="dt-repltext" term="Replacement Text">The <term>replacement 2968: text</term> is the content of the entity, after 2969: replacement of character references and parameter-entity 2970: references. 2971: </termdef> 2972: 2973: The literal entity value 2974: as given in an internal entity declaration 2975: (<nt def="NT-EntityValue">EntityValue</nt>) may contain character, 2976: parameter-entity, and general-entity references. 2977: Such references must be contained entirely within the 2978: literal entity value. 2979: The actual replacement text that is 2980: <termref def="dt-include">included</termref> as described above 2981: must contain the <emph>replacement text</emph> of any 2982: parameter entities referred to, and must contain the character 2983: referred to, in place of any character references in the 2984: literal entity value; however, 2985: general-entity references must be left as-is, unexpanded. 2986: For example, given the following declarations: 2987: 2988: <eg><![CDATA[<!ENTITY % pub "Éditions Gallimard" > 2989: <!ENTITY rights "All rights reserved" > 2990: <!ENTITY book "La Peste: Albert Camus, 2991: © 1947 %pub;. &rights;" >]]></eg> 2992: then the replacement text for the entity "<code>book</code>" is: 2993: <eg>La Peste: Albert Camus, 2994: © 1947 Éditions Gallimard. &rights;</eg> 2995: The general-entity reference "<code>&rights;</code>" would be expanded 2996: should the reference "<code>&book;</code>" appear in the document's 2997: content or an attribute value. 2998: These simple rules may have complex interactions; for a detailed 2999: discussion of a difficult example, see 3000: <specref ref="sec-entexpand"/>. 3001: 3002: 3003: </div2> 3004: <div2 id="sec-predefined-ent"> 3005: <head>Predefined Entities</head> 3006: <termdef id="dt-escape" term="escape">Entity and character 3007: references can both be used to <term>escape</term> the left angle bracket, 3008: ampersand, and other delimiters. A set of general entities 3009: (&magicents;) is specified for this purpose. 3010: Numeric character references may also be used; they are 3011: expanded immediately when recognized and must be treated as 3012: character data, so the numeric character references 3013: "<code>&#60;</code>" and "<code>&#38;</code>" may be used to 3014: escape <code><</code> and <code>&</code> when they occur 3015: in character data.</termdef> 3016: All XML processors must recognize these entities whether they 3017: are declared or not. 3018: <termref def="dt-interop">For interoperability</termref>, 3019: valid XML documents should declare these 3020: entities, like any others, before using them. 3021: If the entities in question are declared, they must be declared 3022: as internal entities whose replacement text is the single 3023: character being escaped or a character reference to 3024: that character, as shown below. 3025: <eg><![CDATA[<!ENTITY lt "&#60;"> 3026: <!ENTITY gt ">"> 3027: <!ENTITY amp "&#38;"> 3028: <!ENTITY apos "'"> 3029: <!ENTITY quot """> 3030: ]]></eg> 3031: Note that the <code><</code> and <code>&</code> characters 3032: in the declarations of "<code>lt</code>" and "<code>amp</code>" 3033: are doubly escaped to meet the requirement that entity replacement 3034: be well-formed. 3035: 3036: </div2> 3037: 3038: <div2 id="Notations"> 3039: <head>Notation Declarations</head> 3040: 3041: <termdef id="dt-notation" term="Notation"><term>Notations</term> identify by 3042: name the format of <termref def="dt-extent">unparsed 3043: entities</termref>, the 3044: format of elements which bear a notation attribute, 3045: or the application to which 3046: a <termref def="dt-pi">processing instruction</termref> is 3047: addressed.</termdef> 3048: <termdef id="dt-notdecl" term="Notation Declaration"> 3049: <term>Notation declarations</term> 3050: provide a name for the notation, for use in 3051: entity and attribute-list declarations and in attribute specifications, 3052: and an external identifier for the notation which may allow an XML 3053: processor or its client application to locate a helper application 3054: capable of processing data in the given notation. 3055: <scrap lang="ebnf"> 3056: <head>Notation Declarations</head> 3057: <prod id="NT-NotationDecl"><lhs>NotationDecl</lhs> 3058: <rhs>'<!NOTATION' <nt def="NT-S">S</nt> <nt def="NT-Name">Name</nt> 3059: <nt def="NT-S">S</nt> 3060: (<nt def="NT-ExternalID">ExternalID</nt> | 3061: <nt def="NT-PublicID">PublicID</nt>) 3062: <nt def="NT-S">S</nt>? '>'</rhs></prod> 3063: <prod id="NT-PublicID"><lhs>PublicID</lhs> 3064: <rhs>'PUBLIC' <nt def="NT-S">S</nt> 3065: <nt def="NT-PubidLiteral">PubidLiteral</nt> 3066: </rhs></prod> 3067: </scrap> 3068: </termdef> 3069: XML processors must provide applications with the name and external 3070: identifier(s) of any notation declared and referred to in an attribute 3071: value, attribute definition, or entity declaration. They may 3072: additionally resolve the external identifier into the 3073: <termref def="dt-sysid">system identifier</termref>, 3074: file name, or other information needed to allow the 3075: application to call a processor for data in the notation described. (It 3076: is not an error, however, for XML documents to declare and refer to 3077: notations for which notation-specific applications are not available on 3078: the system where the XML processor or application is running.) 3079: </div2> 3080: 3081: 3082: <div2 id="sec-doc-entity"> 3083: <head>Document Entity</head> 3084: 3085: <termdef id="dt-docent" term="Document Entity">The <term>document 3086: entity</term> serves as the root of the entity 3087: tree and a starting-point for an <termref def="dt-xml-proc">XML 3088: processor</termref>.</termdef> 3089: This specification does 3090: not specify how the document entity is to be located by an XML 3091: processor; unlike other entities, the document entity has no name and might 3092: well appear on a processor input stream 3093: without any identification at all. 3094: </div2> 3095: 3096: 3097: </div1> 3098:  3099: 3100: <div1 id="sec-conformance"> 3101: <head>Conformance</head> 3102: 3103: <div2 id="proc-types"> 3104: <head>Validating and Non-Validating Processors</head> 3105: Conforming <termref def="dt-xml-proc">XML processors</termref> fall into two 3106: classes: validating and non-validating. 3107: Validating and non-validating processors alike must report 3108: violations of this specification's well-formedness constraints 3109: in the content of the 3110: <termref def="dt-docent">document entity</termref> and any 3111: other <termref def="dt-parsedent">parsed entities</termref> that 3112: they read. 3113: <termdef id="dt-validating" term="Validating Processor"> 3114: <term>Validating processors</term> must report 3115: violations of the constraints expressed by the declarations in the 3116: <termref def="dt-doctype">DTD</termref>, and 3117: failures to fulfill the validity constraints given 3118: in this specification. 3119: </termdef> 3120: To accomplish this, validating XML processors must read and process the entire 3121: DTD and all external parsed entities referenced in the document. 3122: 3123: Non-validating processors are required to check only the 3124: <termref def="dt-docent">document entity</termref>, including 3125: the entire internal DTD subset, for well-formedness. 3126: <termdef id="dt-use-mdecl" term="Process Declarations"> 3127: While they are not required to check the document for validity, 3128: they are required to 3129: <term>process</term> all the declarations they read in the 3130: internal DTD subset and in any parameter entity that they 3131: read, up to the first reference 3132: to a parameter entity that they do <emph>not</emph> read; that is to 3133: say, they must 3134: use the information in those declarations to 3135: <titleref href="AVNormalize">normalize</titleref> attribute values, 3136: <titleref href="included">include</titleref> the replacement text of 3137: internal entities, and supply 3138: <titleref href="sec-attr-defaults">default attribute values</titleref>. 3139: </termdef> 3140: They must not <termref def="dt-use-mdecl">process</termref> 3141: <termref def="dt-entdecl">entity declarations</termref> or 3142: <termref def="dt-attdecl">attribute-list declarations</termref> 3143: encountered after a reference to a parameter entity that is not 3144: read, since the entity may have contained overriding declarations. 3145: 3146: </div2> 3147: <div2 id="safe-behavior"> 3148: <head>Using XML Processors</head> 3149: The behavior of a validating XML processor is highly predictable; it 3150: must read every piece of a document and report all well-formedness and 3151: validity violations. 3152: Less is required of a non-validating processor; it need not read any 3153: part of the document other than the document entity. 3154: This has two effects that may be important to users of XML processors: 3155: <ulist> 3156: <item>Certain well-formedness errors, specifically those that require 3157: reading external entities, may not be detected by a non-validating processor. 3158: Examples include the constraints entitled 3159: <titleref href="wf-entdeclared">Entity Declared</titleref>, 3160: <titleref href="wf-textent">Parsed Entity</titleref>, and 3161: <titleref href="wf-norecursion">No Recursion</titleref>, as well 3162: as some of the cases described as 3163: <titleref href="forbidden">forbidden</titleref> in 3164: <specref ref="entproc"/>.</item> 3165: <item>The information passed from the processor to the application may 3166: vary, depending on whether the processor reads 3167: parameter and external entities. 3168: For example, a non-validating processor may not 3169: <titleref href="AVNormalize">normalize</titleref> attribute values, 3170: <titleref href="included">include</titleref> the replacement text of 3171: internal entities, or supply 3172: <titleref href="sec-attr-defaults">default attribute values</titleref>, 3173: where doing so depends on having read declarations in 3174: external or parameter entities.</item> 3175: </ulist> 3176: 3177: For maximum reliability in interoperating between different XML 3178: processors, applications which use non-validating processors should not 3179: rely on any behaviors not required of such processors. 3180: Applications which require facilities such as the use of default 3181: attributes or internal entities which are declared in external 3182: entities should use validating XML processors. 3183: </div2> 3184: </div1> 3185: 3186: <div1 id="sec-notation"> 3187: <head>Notation</head> 3188: 3189: The formal grammar of XML is given in this specification using a simple 3190: Extended Backus-Naur Form (EBNF) notation. Each rule in the grammar defines 3191: one symbol, in the form 3192: <eg>symbol ::= expression</eg> 3193: Symbols are written with an initial capital letter if they are 3194: defined by a regular expression, or with an initial lower case letter 3195: otherwise. 3196: Literal strings are quoted. 3197: 3198: 3199: 3200: Within the expression on the right-hand side of a rule, the following 3201: expressions are used to match strings of one or more characters: 3202: <glist> 3203: <gitem> 3204: <label><code>#xN</code></label> 3205: <def>where <code>N</code> is a hexadecimal integer, the 3206: expression matches the character in ISO/IEC 10646 whose canonical 3207: (UCS-4) 3208: code value, when interpreted as an unsigned binary number, has 3209: the value indicated. The number of leading zeros in the 3210: <code>#xN</code> form is insignificant; the number of leading 3211: zeros in the corresponding code value 3212: is governed by the character 3213: encoding in use and is not significant for XML.</def> 3214: </gitem> 3215: <gitem> 3216: <label><code>[a-zA-Z]</code>, <code>[#xN-#xN]</code></label> 3217: <def>matches any <termref def="dt-character">character</termref> 3218: with a value in the range(s) indicated (inclusive).</def> 3219: </gitem> 3220: <gitem> 3221: <label><code>[^a-z]</code>, <code>[^#xN-#xN]</code></label> 3222: <def>matches any <termref def="dt-character">character</termref> 3223: with a value <emph>outside</emph> the 3224: range indicated.</def> 3225: </gitem> 3226: <gitem> 3227: <label><code>[^abc]</code>, <code>[^#xN#xN#xN]</code></label> 3228: <def>matches any <termref def="dt-character">character</termref> 3229: with a value not among the characters given.</def> 3230: </gitem> 3231: <gitem> 3232: <label><code>"string"</code></label> 3233: <def>matches a literal string <termref def="dt-match">matching</termref> 3234: that given inside the double quotes.</def> 3235: </gitem> 3236: <gitem> 3237: <label><code>'string'</code></label> 3238: <def>matches a literal string <termref def="dt-match">matching</termref> 3239: that given inside the single quotes.</def> 3240: </gitem> 3241: </glist> 3242: These symbols may be combined to match more complex patterns as follows, 3243: where <code>A</code> and <code>B</code> represent simple expressions: 3244: <glist> 3245: <gitem> 3246: <label>(<code>expression</code>)</label> 3247: <def><code>expression</code> is treated as a unit 3248: and may be combined as described in this list.</def> 3249: </gitem> 3250: <gitem> 3251: <label><code>A?</code></label> 3252: <def>matches <code>A</code> or nothing; optional <code>A</code>.</def> 3253: </gitem> 3254: <gitem> 3255: <label><code>A B</code></label> 3256: <def>matches <code>A</code> followed by <code>B</code>.</def> 3257: </gitem> 3258: <gitem> 3259: <label><code>A | B</code></label> 3260: <def>matches <code>A</code> or <code>B</code> but not both.</def> 3261: </gitem> 3262: <gitem> 3263: <label><code>A - B</code></label> 3264: <def>matches any string that matches <code>A</code> but does not match 3265: <code>B</code>. 3266: </def> 3267: </gitem> 3268: <gitem> 3269: <label><code>A+</code></label> 3270: <def>matches one or more occurrences of <code>A</code>.</def> 3271: </gitem> 3272: <gitem> 3273: <label><code>A*</code></label> 3274: <def>matches zero or more occurrences of <code>A</code>.</def> 3275: </gitem> 3276: 3277: </glist> 3278: Other notations used in the productions are: 3279: <glist> 3280: <gitem> 3281: <label><code>/* ... */</code></label> 3282: <def>comment.</def> 3283: </gitem> 3284: <gitem> 3285: <label><code>[ wfc: ... ]</code></label> 3286: <def>well-formedness constraint; this identifies by name a 3287: constraint on 3288: <termref def="dt-wellformed">well-formed</termref> documents 3289: associated with a production.</def> 3290: </gitem> 3291: <gitem> 3292: <label><code>[ vc: ... ]</code></label> 3293: <def>validity constraint; this identifies by name a constraint on 3294: <termref def="dt-valid">valid</termref> documents associated with 3295: a production.</def> 3296: </gitem> 3297: </glist> 3298: </div1> 3299: 3300: </body> 3301: <back> 3302:  3303: 3304: 3305:  3306: <div1 id="sec-bibliography"> 3307: 3308: <head>References</head> 3309: <div2 id="sec-existing-stds"> 3310: <head>Normative References</head> 3311: 3312: <blist> 3313: <bibl id="IANA" key="IANA"> 3314: (Internet Assigned Numbers Authority) <emph>Official Names for 3315: Character Sets</emph>, 3316: ed. Keld Simonsen et al. 3317: See <loc href="ftp://ftp.isi.edu/in-notes/iana/assignments/character-sets">ftp://ftp.isi.edu/in-notes/iana/assignments/character-sets</loc>. 3318: </bibl> 3319: 3320: <bibl id="RFC1766" key="IETF RFC 1766"> 3321: IETF (Internet Engineering Task Force). 3322: <emph>RFC 1766: Tags for the Identification of Languages</emph>, 3323: ed. H. Alvestrand. 3324: 1995. 3325: </bibl> 3326: 3327: <bibl id="ISO639" key="ISO 639"> 3328: (International Organization for Standardization). 3329: <emph>ISO 639:1988 (E). 3330: Code for the representation of names of languages.</emph> 3331: [Geneva]: International Organization for 3332: Standardization, 1988.</bibl> 3333: 3334: <bibl id="ISO3166" key="ISO 3166"> 3335: (International Organization for Standardization). 3336: <emph>ISO 3166-1:1997 (E). 3337: Codes for the representation of names of countries and their subdivisions 3338: — Part 1: Country codes</emph> 3339: [Geneva]: International Organization for 3340: Standardization, 1997.</bibl> 3341: 3342: <bibl id="ISO10646" key="ISO/IEC 10646">ISO 3343: (International Organization for Standardization). 3344: <emph>ISO/IEC 10646-1993 (E). Information technology — Universal 3345: Multiple-Octet Coded Character Set (UCS) — Part 1: 3346: Architecture and Basic Multilingual Plane.</emph> 3347: [Geneva]: International Organization for 3348: Standardization, 1993 (plus amendments AM 1 through AM 7). 3349: </bibl> 3350: 3351: <bibl id="Unicode" key="Unicode">The Unicode Consortium. 3352: <emph>The Unicode Standard, Version 2.0.</emph> 3353: Reading, Mass.: Addison-Wesley Developers Press, 1996.</bibl> 3354: 3355: </blist> 3356: 3357: </div2> 3358: 3359: <div2><head>Other References</head> 3360: 3361: <blist> 3362: 3363: <bibl id="Aho" key="Aho/Ullman">Aho, Alfred V., 3364: Ravi Sethi, and Jeffrey D. Ullman. 3365: <emph>Compilers: Principles, Techniques, and Tools</emph>. 3366: Reading: Addison-Wesley, 1986, rpt. corr. 1988.</bibl> 3367: 3368: <bibl id="Berners-Lee" xml-link="simple" key="Berners-Lee et al."> 3369: Berners-Lee, T., R. Fielding, and L. Masinter. 3370: <emph>Uniform Resource Identifiers (URI): Generic Syntax and 3371: Semantics</emph>. 3372: 1997. 3373: (Work in progress; see updates to RFC1738.)</bibl> 3374: 3375: <bibl id="ABK" key="Brüggemann-Klein">Brüggemann-Klein, Anne. 3376: <emph>Regular Expressions into Finite Automata</emph>. 3377: Extended abstract in I. Simon, Hrsg., LATIN 1992, 3378: S. 97-98. Springer-Verlag, Berlin 1992. 3379: Full Version in Theoretical Computer Science 120: 197-213, 1993. 3380: 3381: </bibl> 3382: 3383: <bibl id="ABKDW" key="Brüggemann-Klein and Wood">Brüggemann-Klein, Anne, 3384: and Derick Wood. 3385: <emph>Deterministic Regular Languages</emph>. 3386: Universität Freiburg, Institut für Informatik, 3387: Bericht 38, Oktober 1991. 3388: </bibl> 3389: 3390: <bibl id="Clark" key="Clark">James Clark. 3391: Comparison of SGML and XML. See 3392: <loc href="http://www.w3.org/TR/NOTE-sgml-xml-971215">http://www.w3.org/TR/NOTE-sgml-xml-971215</loc>. 3393: </bibl> 3394: <bibl id="RFC1738" xml-link="simple" key="IETF RFC1738"> 3395: IETF (Internet Engineering Task Force). 3396: <emph>RFC 1738: Uniform Resource Locators (URL)</emph>, 3397: ed. T. Berners-Lee, L. Masinter, M. McCahill. 3398: 1994. 3399: </bibl> 3400: 3401: <bibl id="RFC1808" xml-link="simple" key="IETF RFC1808"> 3402: IETF (Internet Engineering Task Force). 3403: <emph>RFC 1808: Relative Uniform Resource Locators</emph>, 3404: ed. R. Fielding. 3405: 1995. 3406: </bibl> 3407: 3408: <bibl id="RFC2141" xml-link="simple" key="IETF RFC2141"> 3409: IETF (Internet Engineering Task Force). 3410: <emph>RFC 2141: URN Syntax</emph>, 3411: ed. R. Moats. 3412: 1997. 3413: </bibl> 3414: 3415: <bibl id="ISO8879" key="ISO 8879">ISO 3416: (International Organization for Standardization). 3417: <emph>ISO 8879:1986(E). Information processing — Text and Office 3418: Systems — Standard Generalized Markup Language (SGML).</emph> First 3419: edition — 1986-10-15. [Geneva]: International Organization for 3420: Standardization, 1986. 3421: </bibl> 3422: 3423: 3424: <bibl id="ISO10744" key="ISO/IEC 10744">ISO 3425: (International Organization for Standardization). 3426: <emph>ISO/IEC 10744-1992 (E). Information technology — 3427: Hypermedia/Time-based Structuring Language (HyTime). 3428: </emph> 3429: [Geneva]: International Organization for 3430: Standardization, 1992. 3431: <emph>Extended Facilities Annexe.</emph> 3432: [Geneva]: International Organization for 3433: Standardization, 1996. 3434: </bibl> 3435: 3436: 3437: 3438: </blist> 3439: </div2> 3440: </div1> 3441: <div1 id="CharClasses"> 3442: <head>Character Classes</head> 3443: Following the characteristics defined in the Unicode standard, 3444: characters are classed as base characters (among others, these 3445: contain the alphabetic characters of the Latin alphabet, without 3446: diacritics), ideographic characters, and combining characters (among 3447: others, this class contains most diacritics); these classes combine 3448: to form the class of letters. Digits and extenders are 3449: also distinguished. 3450: <scrap lang="ebnf" id="CHARACTERS"> 3451: <head>Characters</head> 3452: <prodgroup pcw3="3" pcw4="15"> 3453: <prod id="NT-Letter"><lhs>Letter</lhs> 3454: <rhs><nt def="NT-BaseChar">BaseChar</nt> 3455: | <nt def="NT-Ideographic">Ideographic</nt></rhs> </prod> 3456: <prod id="NT-BaseChar"><lhs>BaseChar</lhs> 3457: <rhs>[#x0041-#x005A] 3458: | [#x0061-#x007A] 3459: | [#x00C0-#x00D6] 3460: | [#x00D8-#x00F6] 3461: | [#x00F8-#x00FF] 3462: | [#x0100-#x0131] 3463: | [#x0134-#x013E] 3464: | [#x0141-#x0148] 3465: | [#x014A-#x017E] 3466: | [#x0180-#x01C3] 3467: | [#x01CD-#x01F0] 3468: | [#x01F4-#x01F5] 3469: | [#x01FA-#x0217] 3470: | [#x0250-#x02A8] 3471: | [#x02BB-#x02C1] 3472: | #x0386 3473: | [#x0388-#x038A] 3474: | #x038C 3475: | [#x038E-#x03A1] 3476: | [#x03A3-#x03CE] 3477: | [#x03D0-#x03D6] 3478: | #x03DA 3479: | #x03DC 3480: | #x03DE 3481: | #x03E0 3482: | [#x03E2-#x03F3] 3483: | [#x0401-#x040C] 3484: | [#x040E-#x044F] 3485: | [#x0451-#x045C] 3486: | [#x045E-#x0481] 3487: | [#x0490-#x04C4] 3488: | [#x04C7-#x04C8] 3489: | [#x04CB-#x04CC] 3490: | [#x04D0-#x04EB] 3491: | [#x04EE-#x04F5] 3492: | [#x04F8-#x04F9] 3493: | [#x0531-#x0556] 3494: | #x0559 3495: | [#x0561-#x0586] 3496: | [#x05D0-#x05EA] 3497: | [#x05F0-#x05F2] 3498: | [#x0621-#x063A] 3499: | [#x0641-#x064A] 3500: | [#x0671-#x06B7] 3501: | [#x06BA-#x06BE] 3502: | [#x06C0-#x06CE] 3503: | [#x06D0-#x06D3] 3504: | #x06D5 3505: | [#x06E5-#x06E6] 3506: | [#x0905-#x0939] 3507: | #x093D 3508: | [#x0958-#x0961] 3509: | [#x0985-#x098C] 3510: | [#x098F-#x0990] 3511: | [#x0993-#x09A8] 3512: | [#x09AA-#x09B0] 3513: | #x09B2 3514: | [#x09B6-#x09B9] 3515: | [#x09DC-#x09DD] 3516: | [#x09DF-#x09E1] 3517: | [#x09F0-#x09F1] 3518: | [#x0A05-#x0A0A] 3519: | [#x0A0F-#x0A10] 3520: | [#x0A13-#x0A28] 3521: | [#x0A2A-#x0A30] 3522: | [#x0A32-#x0A33] 3523: | [#x0A35-#x0A36] 3524: | [#x0A38-#x0A39] 3525: | [#x0A59-#x0A5C] 3526: | #x0A5E 3527: | [#x0A72-#x0A74] 3528: | [#x0A85-#x0A8B] 3529: | #x0A8D 3530: | [#x0A8F-#x0A91] 3531: | [#x0A93-#x0AA8] 3532: | [#x0AAA-#x0AB0] 3533: | [#x0AB2-#x0AB3] 3534: | [#x0AB5-#x0AB9] 3535: | #x0ABD 3536: | #x0AE0 3537: | [#x0B05-#x0B0C] 3538: | [#x0B0F-#x0B10] 3539: | [#x0B13-#x0B28] 3540: | [#x0B2A-#x0B30] 3541: | [#x0B32-#x0B33] 3542: | [#x0B36-#x0B39] 3543: | #x0B3D 3544: | [#x0B5C-#x0B5D] 3545: | [#x0B5F-#x0B61] 3546: | [#x0B85-#x0B8A] 3547: | [#x0B8E-#x0B90] 3548: | [#x0B92-#x0B95] 3549: | [#x0B99-#x0B9A] 3550: | #x0B9C 3551: | [#x0B9E-#x0B9F] 3552: | [#x0BA3-#x0BA4] 3553: | [#x0BA8-#x0BAA] 3554: | [#x0BAE-#x0BB5] 3555: | [#x0BB7-#x0BB9] 3556: | [#x0C05-#x0C0C] 3557: | [#x0C0E-#x0C10] 3558: | [#x0C12-#x0C28] 3559: | [#x0C2A-#x0C33] 3560: | [#x0C35-#x0C39] 3561: | [#x0C60-#x0C61] 3562: | [#x0C85-#x0C8C] 3563: | [#x0C8E-#x0C90] 3564: | [#x0C92-#x0CA8] 3565: | [#x0CAA-#x0CB3] 3566: | [#x0CB5-#x0CB9] 3567: | #x0CDE 3568: | [#x0CE0-#x0CE1] 3569: | [#x0D05-#x0D0C] 3570: | [#x0D0E-#x0D10] 3571: | [#x0D12-#x0D28] 3572: | [#x0D2A-#x0D39] 3573: | [#x0D60-#x0D61] 3574: | [#x0E01-#x0E2E] 3575: | #x0E30 3576: | [#x0E32-#x0E33] 3577: | [#x0E40-#x0E45] 3578: | [#x0E81-#x0E82] 3579: | #x0E84 3580: | [#x0E87-#x0E88] 3581: | #x0E8A 3582: | #x0E8D 3583: | [#x0E94-#x0E97] 3584: | [#x0E99-#x0E9F] 3585: | [#x0EA1-#x0EA3] 3586: | #x0EA5 3587: | #x0EA7 3588: | [#x0EAA-#x0EAB] 3589: | [#x0EAD-#x0EAE] 3590: | #x0EB0 3591: | [#x0EB2-#x0EB3] 3592: | #x0EBD 3593: | [#x0EC0-#x0EC4] 3594: | [#x0F40-#x0F47] 3595: | [#x0F49-#x0F69] 3596: | [#x10A0-#x10C5] 3597: | [#x10D0-#x10F6] 3598: | #x1100 3599: | [#x1102-#x1103] 3600: | [#x1105-#x1107] 3601: | #x1109 3602: | [#x110B-#x110C] 3603: | [#x110E-#x1112] 3604: | #x113C 3605: | #x113E 3606: | #x1140 3607: | #x114C 3608: | #x114E 3609: | #x1150 3610: | [#x1154-#x1155] 3611: | #x1159 3612: | [#x115F-#x1161] 3613: | #x1163 3614: | #x1165 3615: | #x1167 3616: | #x1169 3617: | [#x116D-#x116E] 3618: | [#x1172-#x1173] 3619: | #x1175 3620: | #x119E 3621: | #x11A8 3622: | #x11AB 3623: | [#x11AE-#x11AF] 3624: | [#x11B7-#x11B8] 3625: | #x11BA 3626: | [#x11BC-#x11C2] 3627: | #x11EB 3628: | #x11F0 3629: | #x11F9 3630: | [#x1E00-#x1E9B] 3631: | [#x1EA0-#x1EF9] 3632: | [#x1F00-#x1F15] 3633: | [#x1F18-#x1F1D] 3634: | [#x1F20-#x1F45] 3635: | [#x1F48-#x1F4D] 3636: | [#x1F50-#x1F57] 3637: | #x1F59 3638: | #x1F5B 3639: | #x1F5D 3640: | [#x1F5F-#x1F7D] 3641: | [#x1F80-#x1FB4] 3642: | [#x1FB6-#x1FBC] 3643: | #x1FBE 3644: | [#x1FC2-#x1FC4] 3645: | [#x1FC6-#x1FCC] 3646: | [#x1FD0-#x1FD3] 3647: | [#x1FD6-#x1FDB] 3648: | [#x1FE0-#x1FEC] 3649: | [#x1FF2-#x1FF4] 3650: | [#x1FF6-#x1FFC] 3651: | #x2126 3652: | [#x212A-#x212B] 3653: | #x212E 3654: | [#x2180-#x2182] 3655: | [#x3041-#x3094] 3656: | [#x30A1-#x30FA] 3657: | [#x3105-#x312C] 3658: | [#xAC00-#xD7A3] 3659: </rhs></prod> 3660: <prod id="NT-Ideographic"><lhs>Ideographic</lhs> 3661: <rhs>[#x4E00-#x9FA5] 3662: | #x3007 3663: | [#x3021-#x3029] 3664: </rhs></prod> 3665: <prod id="NT-CombiningChar"><lhs>CombiningChar</lhs> 3666: <rhs>[#x0300-#x0345] 3667: | [#x0360-#x0361] 3668: | [#x0483-#x0486] 3669: | [#x0591-#x05A1] 3670: | [#x05A3-#x05B9] 3671: | [#x05BB-#x05BD] 3672: | #x05BF 3673: | [#x05C1-#x05C2] 3674: | #x05C4 3675: | [#x064B-#x0652] 3676: | #x0670 3677: | [#x06D6-#x06DC] 3678: | [#x06DD-#x06DF] 3679: | [#x06E0-#x06E4] 3680: | [#x06E7-#x06E8] 3681: | [#x06EA-#x06ED] 3682: | [#x0901-#x0903] 3683: | #x093C 3684: | [#x093E-#x094C] 3685: | #x094D 3686: | [#x0951-#x0954] 3687: | [#x0962-#x0963] 3688: | [#x0981-#x0983] 3689: | #x09BC 3690: | #x09BE 3691: | #x09BF 3692: | [#x09C0-#x09C4] 3693: | [#x09C7-#x09C8] 3694: | [#x09CB-#x09CD] 3695: | #x09D7 3696: | [#x09E2-#x09E3] 3697: | #x0A02 3698: | #x0A3C 3699: | #x0A3E 3700: | #x0A3F 3701: | [#x0A40-#x0A42] 3702: | [#x0A47-#x0A48] 3703: | [#x0A4B-#x0A4D] 3704: | [#x0A70-#x0A71] 3705: | [#x0A81-#x0A83] 3706: | #x0ABC 3707: | [#x0ABE-#x0AC5] 3708: | [#x0AC7-#x0AC9] 3709: | [#x0ACB-#x0ACD] 3710: | [#x0B01-#x0B03] 3711: | #x0B3C 3712: | [#x0B3E-#x0B43] 3713: | [#x0B47-#x0B48] 3714: | [#x0B4B-#x0B4D] 3715: | [#x0B56-#x0B57] 3716: | [#x0B82-#x0B83] 3717: | [#x0BBE-#x0BC2] 3718: | [#x0BC6-#x0BC8] 3719: | [#x0BCA-#x0BCD] 3720: | #x0BD7 3721: | [#x0C01-#x0C03] 3722: | [#x0C3E-#x0C44] 3723: | [#x0C46-#x0C48] 3724: | [#x0C4A-#x0C4D] 3725: | [#x0C55-#x0C56] 3726: | [#x0C82-#x0C83] 3727: | [#x0CBE-#x0CC4] 3728: | [#x0CC6-#x0CC8] 3729: | [#x0CCA-#x0CCD] 3730: | [#x0CD5-#x0CD6] 3731: | [#x0D02-#x0D03] 3732: | [#x0D3E-#x0D43] 3733: | [#x0D46-#x0D48] 3734: | [#x0D4A-#x0D4D] 3735: | #x0D57 3736: | #x0E31 3737: | [#x0E34-#x0E3A] 3738: | [#x0E47-#x0E4E] 3739: | #x0EB1 3740: | [#x0EB4-#x0EB9] 3741: | [#x0EBB-#x0EBC] 3742: | [#x0EC8-#x0ECD] 3743: | [#x0F18-#x0F19] 3744: | #x0F35 3745: | #x0F37 3746: | #x0F39 3747: | #x0F3E 3748: | #x0F3F 3749: | [#x0F71-#x0F84] 3750: | [#x0F86-#x0F8B] 3751: | [#x0F90-#x0F95] 3752: | #x0F97 3753: | [#x0F99-#x0FAD] 3754: | [#x0FB1-#x0FB7] 3755: | #x0FB9 3756: | [#x20D0-#x20DC] 3757: | #x20E1 3758: | [#x302A-#x302F] 3759: | #x3099 3760: | #x309A 3761: </rhs></prod> 3762: <prod id="NT-Digit"><lhs>Digit</lhs> 3763: <rhs>[#x0030-#x0039] 3764: | [#x0660-#x0669] 3765: | [#x06F0-#x06F9] 3766: | [#x0966-#x096F] 3767: | [#x09E6-#x09EF] 3768: | [#x0A66-#x0A6F] 3769: | [#x0AE6-#x0AEF] 3770: | [#x0B66-#x0B6F] 3771: | [#x0BE7-#x0BEF] 3772: | [#x0C66-#x0C6F] 3773: | [#x0CE6-#x0CEF] 3774: | [#x0D66-#x0D6F] 3775: | [#x0E50-#x0E59] 3776: | [#x0ED0-#x0ED9] 3777: | [#x0F20-#x0F29] 3778: </rhs></prod> 3779: <prod id="NT-Extender"><lhs>Extender</lhs> 3780: <rhs>#x00B7 3781: | #x02D0 3782: | #x02D1 3783: | #x0387 3784: | #x0640 3785: | #x0E46 3786: | #x0EC6 3787: | #x3005 3788: | [#x3031-#x3035] 3789: | [#x309D-#x309E] 3790: | [#x30FC-#x30FE] 3791: </rhs></prod> 3792: 3793: </prodgroup> 3794: </scrap> 3795: 3796: The character classes defined here can be derived from the 3797: Unicode character database as follows: 3798: <ulist> 3799: <item> 3800: Name start characters must have one of the categories Ll, Lu, 3801: Lo, Lt, Nl. 3802: </item> 3803: <item> 3804: Name characters other than Name-start characters 3805: must have one of the categories Mc, Me, Mn, Lm, or Nd. 3806: </item> 3807: <item> 3808: Characters in the compatibility area (i.e. with character code 3809: greater than #xF900 and less than #xFFFE) are not allowed in XML 3810: names. 3811: </item> 3812: <item> 3813: Characters which have a font or compatibility decomposition (i.e. those 3814: with a "compatibility formatting tag" in field 5 of the database -- 3815: marked by field 5 beginning with a "<") are not allowed. 3816: </item> 3817: <item> 3818: The following characters are treated as name-start characters 3819: rather than name characters, because the property file classifies 3820: them as Alphabetic: [#x02BB-#x02C1], #x0559, #x06E5, #x06E6. 3821: </item> 3822: <item> 3823: Characters #x20DD-#x20E0 are excluded (in accordance with 3824: Unicode, section 5.14). 3825: </item> 3826: <item> 3827: Character #x00B7 is classified as an extender, because the 3828: property list so identifies it. 3829: </item> 3830: <item> 3831: Character #x0387 is added as a name character, because #x00B7 3832: is its canonical equivalent. 3833: </item> 3834: <item> 3835: Characters ':' and '_' are allowed as name-start characters. 3836: </item> 3837: <item> 3838: Characters '-' and '.' are allowed as name characters. 3839: </item> 3840: </ulist> 3841: 3842: </div1> 3843: <inform-div1 id="sec-xml-and-sgml"> 3844: <head>XML and SGML</head> 3845: 3846: XML is designed to be a subset of SGML, in that every 3847: <termref def="dt-valid">valid</termref> XML document should also be a 3848: conformant SGML document. 3849: For a detailed comparison of the additional restrictions that XML places on 3850: documents beyond those of SGML, see <bibref ref="Clark"/>. 3851: 3852: </inform-div1> 3853: <inform-div1 id="sec-entexpand"> 3854: <head>Expansion of Entity and Character References</head> 3855: This appendix contains some examples illustrating the 3856: sequence of entity- and character-reference recognition and 3857: expansion, as specified in <specref ref="entproc"/>. 3858: 3859: If the DTD contains the declaration 3860: <eg><![CDATA[<!ENTITY example "An ampersand (&#38;) may be escaped 3861: numerically (&#38;#38;) or with a general entity 3862: (&amp;)." > 3863: ]]></eg> 3864: then the XML processor will recognize the character references 3865: when it parses the entity declaration, and resolve them before 3866: storing the following string as the 3867: value of the entity "<code>example</code>": 3868: <eg><![CDATA[An ampersand (&) may be escaped 3869: numerically (&#38;) or with a general entity 3870: (&amp;). 3871: ]]></eg> 3872: A reference in the document to "<code>&example;</code>" 3873: will cause the text to be reparsed, at which time the 3874: start- and end-tags of the "<code>p</code>" element will be recognized 3875: and the three references will be recognized and expanded, 3876: resulting in a "<code>p</code>" element with the following content 3877: (all data, no delimiters or markup): 3878: <eg><![CDATA[An ampersand (&) may be escaped 3879: numerically (&) or with a general entity 3880: (&). 3881: ]]></eg> 3882: 3883: A more complex example will illustrate the rules and their 3884: effects fully. In the following example, the line numbers are 3885: solely for reference. 3886: <eg><![CDATA[1 <?xml version='1.0'?> 3887: 2 <!DOCTYPE test [ 3888: 3 <!ELEMENT test (#PCDATA) > 3889: 4 <!ENTITY % xx '%zz;'> 3890: 5 <!ENTITY % zz '<!ENTITY tricky "error-prone" >' > 3891: 6 %xx; 3892: 7 ]> 3893: 8 <test>This sample shows a &tricky; method.</test> 3894: ]]></eg> 3895: This produces the following: 3896: <ulist spacing="compact"> 3897: <item>in line 4, the reference to character 37 is expanded immediately, 3898: and the parameter entity "<code>xx</code>" is stored in the symbol 3899: table with the value "<code>%zz;</code>". Since the replacement text 3900: is not rescanned, the reference to parameter entity "<code>zz</code>" 3901: is not recognized. (And it would be an error if it were, since 3902: "<code>zz</code>" is not yet declared.)</item> 3903: <item>in line 5, the character reference "<code>&#60;</code>" is 3904: expanded immediately and the parameter entity "<code>zz</code>" is 3905: stored with the replacement text 3906: "<code><!ENTITY tricky "error-prone" ></code>", 3907: which is a well-formed entity declaration.</item> 3908: <item>in line 6, the reference to "<code>xx</code>" is recognized, 3909: and the replacement text of "<code>xx</code>" (namely 3910: "<code>%zz;</code>") is parsed. The reference to "<code>zz</code>" 3911: is recognized in its turn, and its replacement text 3912: ("<code><!ENTITY tricky "error-prone" ></code>") is parsed. 3913: The general entity "<code>tricky</code>" has now been 3914: declared, with the replacement text "<code>error-prone</code>".</item> 3915: <item> 3916: in line 8, the reference to the general entity "<code>tricky</code>" is 3917: recognized, and it is expanded, so the full content of the 3918: "<code>test</code>" element is the self-describing (and ungrammatical) string 3919: <emph>This sample shows a error-prone method.</emph> 3920: </item> 3921: </ulist> 3922: 3923: </inform-div1> 3924: <inform-div1 id="determinism"> 3925: <head>Deterministic Content Models</head> 3926: <termref def="dt-compat">For compatibility</termref>, it is 3927: required 3928: that content models in element type declarations be deterministic. 3929: 3930:  3931: SGML 3932: requires deterministic content models (it calls them 3933: "unambiguous"); XML processors built using SGML systems may 3934: flag non-deterministic content models as errors. 3935: For example, the content model <code>((b, c) | (b, d))</code> is 3936: non-deterministic, because given an initial <code>b</code> the parser 3937: cannot know which <code>b</code> in the model is being matched without 3938: looking ahead to see which element follows the <code>b</code>. 3939: In this case, the two references to 3940: <code>b</code> can be collapsed 3941: into a single reference, making the model read 3942: <code>(b, (c | d))</code>. An initial <code>b</code> now clearly 3943: matches only a single name in the content model. The parser doesn't 3944: need to look ahead to see what follows; either <code>c</code> or 3945: <code>d</code> would be accepted. 3946: More formally: a finite state automaton may be constructed from the 3947: content model using the standard algorithms, e.g. algorithm 3.5 3948: in section 3.9 3949: of Aho, Sethi, and Ullman <bibref ref="Aho"/>. 3950: In many such algorithms, a follow set is constructed for each 3951: position in the regular expression (i.e., each leaf 3952: node in the 3953: syntax tree for the regular expression); 3954: if any position has a follow set in which 3955: more than one following position is 3956: labeled with the same element type name, 3957: then the content model is in error 3958: and may be reported as an error. 3959: 3960: Algorithms exist which allow many but not all non-deterministic 3961: content models to be reduced automatically to equivalent deterministic 3962: models; see Brüggemann-Klein 1991 <bibref ref="ABK"/>. 3963: </inform-div1> 3964: <inform-div1 id="sec-guessing"> 3965: <head>Autodetection of Character Encodings</head> 3966: The XML encoding declaration functions as an internal label on each 3967: entity, indicating which character encoding is in use. Before an XML 3968: processor can read the internal label, however, it apparently has to 3969: know what character encoding is in use—which is what the internal label 3970: is trying to indicate. In the general case, this is a hopeless 3971: situation. It is not entirely hopeless in XML, however, because XML 3972: limits the general case in two ways: each implementation is assumed 3973: to support only a finite set of character encodings, and the XML 3974: encoding declaration is restricted in position and content in order to 3975: make it feasible to autodetect the character encoding in use in each 3976: entity in normal cases. Also, in many cases other sources of information 3977: are available in addition to the XML data stream itself. 3978: Two cases may be distinguished, 3979: depending on whether the XML entity is presented to the 3980: processor without, or with, any accompanying 3981: (external) information. We consider the first case first. 3982: 3983: 3984: Because each XML entity not in UTF-8 or UTF-16 format <emph>must</emph> 3985: begin with an XML encoding declaration, in which the first characters 3986: must be '<code><?xml</code>', any conforming processor can detect, 3987: after two to four octets of input, which of the following cases apply. 3988: In reading this list, it may help to know that in UCS-4, '<' is 3989: "<code>#x0000003C</code>" and '?' is "<code>#x0000003F</code>", and the Byte 3990: Order Mark required of UTF-16 data streams is "<code>#xFEFF</code>". 3991: 3992: <ulist> 3993: <item> 3994: <code>00 00 00 3C</code>: UCS-4, big-endian machine (1234 order) 3995: </item> 3996: <item> 3997: <code>3C 00 00 00</code>: UCS-4, little-endian machine (4321 order) 3998: </item> 3999: <item> 4000: <code>00 00 3C 00</code>: UCS-4, unusual octet order (2143) 4001: </item> 4002: <item> 4003: <code>00 3C 00 00</code>: UCS-4, unusual octet order (3412) 4004: </item> 4005: <item> 4006: <code>FE FF</code>: UTF-16, big-endian 4007: </item> 4008: <item> 4009: <code>FF FE</code>: UTF-16, little-endian 4010: </item> 4011: <item> 4012: <code>00 3C 00 3F</code>: UTF-16, big-endian, no Byte Order Mark 4013: (and thus, strictly speaking, in error) 4014: </item> 4015: <item> 4016: <code>3C 00 3F 00</code>: UTF-16, little-endian, no Byte Order Mark 4017: (and thus, strictly speaking, in error) 4018: </item> 4019: <item> 4020: <code>3C 3F 78 6D</code>: UTF-8, ISO 646, ASCII, some part of ISO 8859, 4021: Shift-JIS, EUC, or any other 7-bit, 8-bit, or mixed-width encoding 4022: which ensures that the characters of ASCII have their normal positions, 4023: width, 4024: and values; the actual encoding declaration must be read to 4025: detect which of these applies, but since all of these encodings 4026: use the same bit patterns for the ASCII characters, the encoding 4027: declaration itself may be read reliably 4028: 4029: </item> 4030: <item> 4031: <code>4C 6F A7 94</code>: EBCDIC (in some flavor; the full 4032: encoding declaration must be read to tell which code page is in 4033: use) 4034: </item> 4035: <item> 4036: other: UTF-8 without an encoding declaration, or else 4037: the data stream is corrupt, fragmentary, or enclosed in 4038: a wrapper of some kind 4039: </item> 4040: </ulist> 4041: 4042: 4043: This level of autodetection is enough to read the XML encoding 4044: declaration and parse the character-encoding identifier, which is 4045: still necessary to distinguish the individual members of each family 4046: of encodings (e.g. to tell UTF-8 from 8859, and the parts of 8859 4047: from each other, or to distinguish the specific EBCDIC code page in 4048: use, and so on). 4049: 4050: 4051: Because the contents of the encoding declaration are restricted to 4052: ASCII characters, a processor can reliably read the entire encoding 4053: declaration as soon as it has detected which family of encodings is in 4054: use. Since in practice, all widely used character encodings fall into 4055: one of the categories above, the XML encoding declaration allows 4056: reasonably reliable in-band labeling of character encodings, even when 4057: external sources of information at the operating-system or 4058: transport-protocol level are unreliable. 4059: 4060: 4061: Once the processor has detected the character encoding in use, it can 4062: act appropriately, whether by invoking a separate input routine for 4063: each case, or by calling the proper conversion function on each 4064: character of input. 4065: 4066: 4067: Like any self-labeling system, the XML encoding declaration will not 4068: work if any software changes the entity's character set or encoding 4069: without updating the encoding declaration. Implementors of 4070: character-encoding routines should be careful to ensure the accuracy 4071: of the internal and external information used to label the entity. 4072: 4073: The second possible case occurs when the XML entity is accompanied 4074: by encoding information, as in some file systems and some network 4075: protocols. 4076: When multiple sources of information are available, 4077: 4078: their relative 4079: priority and the preferred method of handling conflict should be 4080: specified as part of the higher-level protocol used to deliver XML. 4081: Rules for the relative priority of the internal label and the 4082: MIME-type label in an external header, for example, should be part of the 4083: RFC document defining the text/xml and application/xml MIME types. In 4084: the interests of interoperability, however, the following rules 4085: are recommended. 4086: <ulist> 4087: <item>If an XML entity is in a file, the Byte-Order Mark 4088: and encoding-declaration PI are used (if present) to determine the 4089: character encoding. All other heuristics and sources of information 4090: are solely for error recovery. 4091: </item> 4092: <item>If an XML entity is delivered with a 4093: MIME type of text/xml, then the <code>charset</code> parameter 4094: on the MIME type determines the 4095: character encoding method; all other heuristics and sources of 4096: information are solely for error recovery. 4097: </item> 4098: <item>If an XML entity is delivered 4099: with a 4100: MIME type of application/xml, then the Byte-Order Mark and 4101: encoding-declaration PI are used (if present) to determine the 4102: character encoding. All other heuristics and sources of 4103: information are solely for error recovery. 4104: </item> 4105: </ulist> 4106: These rules apply only in the absence of protocol-level documentation; 4107: in particular, when the MIME types text/xml and application/xml are 4108: defined, the recommendations of the relevant RFC will supersede 4109: these rules. 4110: 4111: 4112: </inform-div1> 4113: 4114: <inform-div1 id="sec-xml-wg"> 4115: <head>W3C XML Working Group</head> 4116: 4117: This specification was prepared and approved for publication by the 4118: W3C XML Working Group (WG). WG approval of this specification does 4119: not necessarily imply that all WG members voted for its approval. 4120: The current and former members of the XML WG are: 4121: 4122: <orglist> 4123: <member><name>Jon Bosak, Sun</name><role>Chair</role></member> 4124: <member><name>James Clark</name><role>Technical Lead</role></member> 4125: <member><name>Tim Bray, Textuality and Netscape</name><role>XML Co-editor</role></member> 4126: <member><name>Jean Paoli, Microsoft</name><role>XML Co-editor</role></member> 4127: <member><name>C. M. Sperberg-McQueen, U. of Ill.</name><role>XML 4128: Co-editor</role></member> 4129: <member><name>Dan Connolly, W3C</name><role>W3C Liaison</role></member> 4130: <member><name>Paula Angerstein, Texcel</name></member> 4131: <member><name>Steve DeRose, INSO</name></member> 4132: <member><name>Dave Hollander, HP</name></member> 4133: <member><name>Eliot Kimber, ISOGEN</name></member> 4134: <member><name>Eve Maler, ArborText</name></member> 4135: <member><name>Tom Magliery, NCSA</name></member> 4136: <member><name>Murray Maloney, Muzmo and Grif</name></member> 4137: <member><name>Makoto Murata, Fuji Xerox Information Systems</name></member> 4138: <member><name>Joel Nava, Adobe</name></member> 4139: <member><name>Conleth O'Connell, Vignette</name></member> 4140: <member><name>Peter Sharpe, SoftQuad</name></member> 4141: <member><name>John Tigue, DataChannel</name></member> 4142: </orglist> 4143: 4144: </inform-div1> 4145: </back> 4146: </spec> 4147: